Annuals, biennials, perennials, subshrubs, shrubs, vines, or trees. Roots usually taproots, sometimes fibrous. Stems usually erect, sometimes prostrate to ascending (underground stems sometimes woody caudices or rhizomes, sometimes fleshy). Leaves usually alternate or opposite, sometimes in basal rosettes, rarely in whorls; rarely stipulate, usually petiolate, sometimes sessile, sometimes with bases decurrent onto stems; blades usually simple (margins sometimes 1–2+ times pinnatifid or palmatifid), rarely compound. Inflorescences indeterminate heads (also called capitula); each head usually comprising a surrounding involucre of phyllaries (involucral bracts), a receptacle, and (1–)5–300+ florets; individual heads sessile or each borne on a peduncle; heads borne singly or in usually determinate, rarely indeterminate, arrays (cymiform, corymbiform, racemiform, spiciform, etc.); involucres sometimes subtended by calyculi (sing. calyculus); phyllaries borne in 1–5(–15+) series proximal to (i.e., outside of or abaxial to) the florets; receptacles usually flat to convex, sometimes conic or columnar, either paleate (bearing paleae or receptacular bracts that individually subtend some or all of the florets) or epaleate (lacking paleae); epaleate receptacles sometimes bristly or hairy or bearing subulate enations among the florets. Florets bisexual, pistillate, functionally staminate, or neuter (also called neutral); sepals highly modifed (instead of ordinary sepals, each ovary usually bears a pappus of bristles, awns, and/or scales, sometimes in combination within a single pappus); petals connate, corollas (3–)5-merous, ± actinomorphic or zygomorphic (one or both kinds in a single head, see descriptions of radiate, discoid, liguliflorous, disciform, and radiant following); stamens (4–)5, alternate with corolla lobes, filaments inserted on corollas, usually distinct, anthers introrse, usually connate and forming tubes around styles (rarely filaments connate and anthers distinct; e.g., Heliantheae, Ambrosiinae); ovaries inferior, 2-carpellate, and 1-locular with 1 basally attached, anatropous ovule; styles 1 in each bisexual, functionally staminate, or pistillate floret; each style usually ringed at base by a nectary, distally 2-branched with stigmatic papillae borne on adaxial face of each branch in 2 separate or contiguous lines or in 1 continuous band (styles usually not branched in functionally staminate florets), style branches apically truncate or appendaged beyond the stigmatic bands or lines, appendages usually papillate to hirsute distally on abaxial (or abaxial and adaxial) faces. Fruits (technically cypselae, historically called achenes) usually dry with relatively thick, tough pericarps, sometimes beaked (rostrate) and/or winged (alate), often dispersed with aid from pappi. Seeds 1 per fruit, exalbuminous; embryos straight.

Distribution

Nearly worldwide, especially rich in numbers of species and/or in numbers of plants in arid and semiarid regions of subtropical and lower to middle temperate latitudes.

Discussion

Genera ca. 1500, species ca. 23,000 (418 genera, 2413 species in the flora).

Asteraceae (Compositae, “composites,” or “comps”) have long been recognized as a natural group, and circumscription of the group has never been controversial (although some authors have divided the traditional family into three or more families). A. Cronquist (1981) placed Asteraceae as the only family in the order Asterales within subclass Asteridae, associated with the Gentianales, Rubiales, Dipsacales, and Calycerales and relatively distant from Campanulales. On recent molecular phylogenetic data, the Angiosperm Phylogeny Group (2003; see references there for details; classification abbreviated APGII hereafter) has suggested that Asteraceae are better treated as part of a more widely defined Asterales within the asterids II informal clade (or campanulid clade; see W. S. Judd and R. G. Olmstead 2004). Judd and Olmstead summarized the higher-order relationships of Asteraceae as follows (in order of decreasing inclusiveness; synapomorphies in parentheses): asterids (ovules unitegmic and tenuinucellate, iridoid chemistry); core asterids (sympetaly, stamen number equal to petal number, stamen epipetaly, mostly 2–3-carpellate gynoecia); campanulids (early sympetaly), comprising eight unassigned families plus Aquifoliales, which is sister to Dipsacales, Apiales, and Asterales (last three sharing frequently inferior ovaries, polyacetylenes); and Asterales, which appears to be sister to Dipsacales-Apiales (K. Bremer et al. 2004). The order Asterales (valvate petals, lack of apotracheal parenchyma, storage of inulin, ellagic acid present, and, possibly, the presence of a plunger or brush pollen presentation mechanism) now includes the following families (fide APGII): Alseuosmiaceae, Argophyllaceae, Calyceraceae, Campanulaceae (optionally including Lobeliaceae), Goodeniaceae, Menyanthaceae, Pentaphragmaceae, Phellinaceae, Rousseauaceae, and Stylidiaceae. Within Asterales, Asteraceae is part of a clade (corollas with more or less fused lateral veins joining midvein near lobe apices, thick integuments, no endosperm haustorium) with the Menyanthaceae (cosmopolitan with Southern Hemisphere genera) basal to a more nested clade (inferior ovaries, possibly connate anthers, pollen exine with bifurcating columellae) comprising Asteraceae, Goodeniaceae (mainly Australia), and Calyceraceae (South America), the last being the immediate sister to Asteraceae (highly modified, persistent calyces, corolla venation patterns, unilocular and uniovulate gynoecia, pollen with intercolpar depressions, specialized fruits). Aggregation of flowers into heads with involucres appears to have been a parallel phenomenon in Calyceraceae and Asteraceae, given the determinate nature of the former and indeterminate (racemose) organization of the latter. Some traits typical of Asteraceae predate evolution of the family as a distinct clade. Relationships of Asteraceae and Calyceraceae have been discussed by M. H. G. Gustafsson and Bremer (1995). Synapomorphies of the Asteraceae clade include: calyces modified to structures called pappi, anthers connate (forming tubes) and styles modified to function as brushes in a specialized pollen presentation mechanism, ovaries each containing a single basal ovule, and production of sesquiterpene lactones.

K. Bremer et al. (2004) gave an Early Cretaceous origin for the Asteridae and the basal campanulids, and a Late Cretaceous origin for the Asterales. Bremer and M. H. G. Gustafsson (1997) also hypothesized a Late Cretaceous ancestry of Asterales in East Gondwanaland (Australasia), with later expansion into West Gondwanaland (South America-Antarctica), where the Asteraceae originated before the final separation of South America and Antarctica. Similarly, M. L. DeVore and T. F. Stuessy (1995) argued that the close relationships of Asteraceae to Goodeniaceae and Calyceraceae, plus the basal position of Barnadesioideae K. Bremer & R. K. Jansen (Asteraceae), indicated a South America-Antarctica-Australia origin for the complex. After reviewing previous hypotheses, they proposed a late Eocene origin for the complex and suggested a South American origin for the Asteraceae based on the basal position of the South American Barnadesioideae (see also Stuessy et al. 1996, on Barnadesioideae origin in southern South America in the Oligocene) and their sister relationship to Calyceraceae. Fossil pollen data (both Mutisieae and Asteroideae types—notably Heliantheae in the broad sense—among earliest reports) reviewed by A. Graham (1996) appear to indicate an Eocene origin for Asteraceae in South America, with migration to North America at least by the Oligocene, possibly as early as the late Eocene. More recently, M. S. Zavada and S. E. de Villiers (2000; and references therein) reported Asteraceae pollen (assignable to Mutisieae in the broad sense) from the Paleocene-Eocene of South Africa, suggesting an earlier, West Gondwana (southern Africa or Australia) origin for the family. Such data indicate that some tribes of Asteraceae may have arrived in North America via long-distance dispersal or island hopping well before closure of the isthmus of Panama. They also have a bearing on the possible times of radiation of some tribes in North America, particularly Heliantheae in the broad sense and Eupatorieae, which originated in the continent (including Mexico and parts of Central America), and those that came to North America from or through South America such as Mutisieae, Vernonieae, some Plucheeae, and Astereae. Other tribes, such as Cynareae, Cichorieae, some Gnaphalieae, and Anthemideae, may have reached North America from Eurasia, possibly via Beringia (or as Amphi-Atlantic disjuncts), at a later time.

The bases of a tribal classification within Asteraceae were established in the nineteenth century, primarily through the work of H. Cassini (especially in articles scattered through the 61 volumes of F. Cuvier 1816–1845; Cassini included synopses of his tribes as part of his entry for Zoegea, i.e., zyégée in French; the articles have been collected in three volumes by R. M. King and H. W. Dawson 1975), C. F. Lessing (1832), A. P. de Candolle (1828–1838, 1836–1838), and, particularly, G. Bentham (1873). In the twentieth century, the tribal system of Cassini, as elaborated by Bentham, was widely followed with only slight modifications (see S. Carlquist 1976; A. Cronquist 1955, 1977; C. Jeffrey 1978; G. Wagenitz 1976b; see also J. Small 1919 and, for alternate views on Heliantheae-Eupatorieae, H. Robinson 1996).

A molecular phylogenetic study by R. K. Jansen and J. D. Palmer (1987) established that a South American clade (later named Barnadesioideae) is basal within Asteraceae. Both cladistic morphologic analyses (e.g., K. Bremer 1994, 1996) and mostly chloroplast-DNA molecular phylogenies (e.g., Jansen et al. 1991, 1992; K. J. Kim et al. 1992; Kim and Jansen 1995; R. J. Bayer and J. R. Starr 1998; P. K. Eldenäs et al. 1999; B. G. Baldwin et al. 2002) have deepened our knowledge of tribal interrelationships within Asteraceae and led to the recent proposal of a phylogenetic classification for the family with 10 subfamilies and 35 tribes (J. L. Panero and V. A. Funk 2002).

Treatment of Asteraceae here differs from some of the recently proposed classifications in that some groups continue to be traditionally circumscribed (e.g., Mutisieae in the broad sense, Heliantheae in the broad sense, including Helenieae and excluding Eupatorieae). Where appropriate and so far as practicable, new taxonomies are acknowledged in our discussions of individual tribes (which see). In North America, the following subfamilies and tribes, as defined by J. L. Panero and V. A. Funk (2002), are represented (tribes with no native representatives are marked by asterisks): Mutisioideae-Mutisieae in the strict sense, Gochnatioideae-Gochnatieae, and Hecastocleioideae-Hecastocleideae (all included in Mutisieae here, which see), Carduoideae (Cardueae = Cynareae), Cichorioideae (*Arctoteae, Cichorieae, Vernonieae), and Asteroideae [Senecioneae, *Calenduleae, Gnaphalieae, Anthemideae, Astereae, Plucheeae, *Inuleae, Eupatorieae, and the following segregates of Heliantheae in the broad sense (all treated here within or as subtribes of a fairly traditionally circumscribed Heliantheae): Bahieae, Chaenactideae, Coreopsideae, Helenieae, Heliantheae in the strict sense, Madieae, *Millereae, Perityleae, Polymnieae, and Tageteae)].

Asa Gray produced the first broadly influential floristic synthesis of North American Asteraceae. Other authors who made important contributions to floristics of North American Asteraceae in the nineteenth and first half of the twentieth centuries were S. F. Blake, N. L. Britton, R. S. Ferris, M. L. Fernald, E. L. Greene, H. M. Hall, M. E. Jones, D. D. Keck, P. A. Rydberg, J. K. Small, and S. Watson. Some of those authors had narrower concepts of genera and species than had their predecessors and they freely recognized new taxa in Asteraceae (mostly genera and species). Floristics of North American Asteraceae in the second half of the twentieth century was especially influenced by A. Cronquist (e.g., 1955, 1980, 1994; H. A. Gleason and Cronquist 1991), who usually favored traditional generic circumscriptions.

In the last 20 years or so, developments in molecular systematics have led to revisions of generic limits in some tribes of Asteraceae and, sometimes, to a return to generic concepts that had been suggested earlier but largely ignored. More or less worldwide, taxonomies in some tribes or parts of tribes have included segregate genera that have been revived or newly published. Most of the innovations will be summarized in the forthcoming Asterales volume of K. Kubitzki et al. (1990+). The generic circumscriptions adopted here incorporate recent taxonomic findings relevant to North America, insofar as our contributors have accepted them. As a result, many of the genera treated herein have never been presented in a major flora before, and some species are included within genera with which they were not associated traditionally. Thus, the Flora brings together much new knowledge and many new names. In most instances, circumscriptions of species have turned out to be conventional. So far as practicable, recently named species from North America have been accounted for within relevant treatments herein.

With 418 genera and 2413 species (Table 1), Asteraceae is, numerically, the largest family in the flora of North America north of Mexico. Members of the family are found in diverse habitats, from the High Arctic tundra and polar deserts to the Sonoran warm-desert scrub, and from alpine habitats to salt marshes. Asteraceae are particularly conspicuous elements of warm-desert and intermountain grasslands, as well as of desert scrubs, notably the intermountain desert scrub where Artemisia dominates (M. G. Barbour and N. L. Christensen 1993). Among other conspicuous species, members of Solidago and Symphyotrichum form a very showy part of the fall flowering in eastern North America, and members of Heliantheae sometimes produce striking displays in the American West (e.g., Gaillardia spp., Lasthenia spp., members of Madiinae).

Much has been published, not only on systematics (at various levels), but on biology, chemistry, and economic and medical uses of Asteraceae worldwide, particularly in proceedings (from conferences and symposia) edited by V. H. Heywood et al. (1977), T. J. Mabry and G. Wagenitz (1990), and D. J. N. Hind et al. (1995, 1996).

Relatively few North American species of Asteraceae are economically important or widely used ethnobotanically. The only major Asteraceae crop of North American origin is the sunflower, Helianthus annuus, which is valued for its seed oil and is appreciated in the horticultural trade. Other crop plants from native species worth mention are Helianthus tuberosus, the Jerusalem artichoke, and Parthenium argentatum, the guayule, a source of rubber. Echinacea spp. are touted as health plants. Members of several genera of Asteraceae native to the flora are grown for their ornamental value, notably species of Coreopsis (tickseeds), Echinacea (coneflowers), Helianthus (sunflowers), Liatris (blazingstars and gayfeathers), Rudbeckia (black-eyed Susans), Solidago (goldenrods), and Symphyotrichum (“asters” of the trade).

Many species of Asteraceae have been introduced into North America, mainly from Europe and Asia, some deliberately for medicines, foods, or horticulture, others accidentally (often with seeds or other agricultural products or by other means). Few, if any, of the introduced taxa are thought to be noxious at the continental level, but some (e.g., Acroptilon) are considered noxious in large parts of their ranges within the flora. Taraxacum officinale is a common lawn weed that (in terms of dollars spent and herbicides applied in weed control) has an economic and ecologic impact disproportionate to the actual harm it causes; other weedy introduced Asteraceae are of little economic consequence. Some native Asteraceae are toxic to cattle and other livestock and are therefore considered weeds. And some native species of open habitats (e.g., Symphyotrichum pilosum) are often considered weeds because they invade fields left fallow. Ragweeds (especially Ambrosia artemisiifolia and A. trifida) range over nearly the whole continent and their wind-blown pollens cause late–summer allergic reactions (hayfever) for a large number of people. Because ragweeds have a large impact on human health, they have a significant, negative economic impact.

In contrast to Orchidaceae, for which a wealth of excellent, well-illustrated popular books are available, few popular field guides on Asteraceae of North America have been published. The guide by T. M. Antonio and S. Masi (2001) deserves notice for its maps, color photographs, and useful information.

Composites (members of Asteraceae) share some unusual morphologic traits and some morphologic terms are used in particular ways as applied here to them.

For treatments of composites here, “perennials” are herbaceous and differ from annuals and biennials in living longer than two years and differ from subshrubs, shrubs, and trees in not developing woody aerial stems.

In most composites, leaf venation comprises a midrib plus more or less equal lateral nerves or veins; such leaves are described as pinnately nerved. Venation in leaf blades of some composites often consists of a midrib plus relatively strong lateral veins that diverge at or just distal to bases of blades. Such leaves are described as 3-nerved, 3(–5)-nerved, 5-nerved, etc., and, as appropriate, the phrases “from bases” or “distal to bases” may be added for clarification.

Composites often have subsessile to sessile or sunken glandular hairs that consist of multicellular bases supporting globular elements that usually contain resinous or sticky substances. Such structures have been called glands, glandular hairs, glandular trichomes, punctae, resin dots, and so on. Sometimes, the glands are embedded in epidermal depressions or pits. Epidermes with glands more or less sunk into or embedded within the surface have been called glandular-punctate and/or punctate-glandular. The glands may be colorless (translucent) or yellowish to dark brown or orange and are sometimes more prominent on dried specimens than in living plants. In keys and descriptions here, gland-dotted refers to the presence of such glandular hairs, whether sessile or in depressions or pits (as appropriate, “in pits” or “sessile” may be added for clarification).

Inflorescences of composites are called heads (or capitula, sing. capitulum). Heads may be borne singly (i.e., not clearly associated with other heads on the same plant) or associated in arrays. The arrays of heads on composites correspond to arrays of individual flowers (inflorescences) on plants of other families; arrays of heads are sometimes called capitulescences. Terms for architectural structures of arrays of heads are parallel to terms for kinds of inflorescences: cymiform, corymbiform, paniculiform, racemiform, spiciform, thyrsiform, etc.

In radiate heads, peripheral florets (ray florets) in one or more series have corollas with zygomorphic limbs and may be pistillate, or styliferous and sterile, or neuter; the central florets (disc florets) in radiate heads have ± actinomorphic corollas and may be bisexual or functionally staminate. In liguliflorous heads, all florets are bisexual and (usually) fertile and have zygomorphic corollas (ligulate florets); liguliflorous heads are characteristic of Cichorieae and are found in no other composites. In discoid heads, all florets have ± actinomorphic corollas and all are either bisexual and fertile or all are either functionally staminate or pistillate (in monoecious or dioecious taxa, e.g., Baccharis spp.). In disciform heads, all florets have ± actinomorphic corollas, and peripheral florets (in one or more series) are usually pistillate and usually have relatively slender (often filiform) corollas. Such peripheral pistillate florets are generally thought to be derived by reduction from ray florets, and plants with disciform heads are generally thought to be derived from ancestors with radiate heads. The central florets of disciform heads are usually bisexual, sometimes functionally staminate. By tradition and for simplicity, both the peripheral, pistillate florets and the inner, bisexual or functionally staminate florets in disciform heads may be referred to as “disc” florets. In radiant heads, all florets have ± actinomorphic corollas and the peripheral florets usually have much enlarged corollas and may be bisexual, pistillate, or neuter; the central florets of radiant heads are usually bisexual. Some composites have peripheral, bisexual florets with slightly to strongly zygomorphic corollas (e.g., some members of Chaenactis, Lessingia, Thymophylla, et al.); heads of such plants do not quite conform to any of the five types just described and such heads may be referred to as “quasi-radiate” or “quasi-radiant.” Some florets in heads of some Mutisieae have 2-lipped corollas and those heads may be called “quasi-radiate” or “quasi-liguliflorous.” The term eradiate is used to refer collectively to discoid, disciform, and radiant heads.

Heads with all florets of one sexual form (bisexual, pistillate, or functionally staminate) are called homogamous (discoid and liguliflorous heads are homogamous, some radiant heads may be homogamous) and heads with florets of two or more sexual forms are called heterogamous (radiate and disciform heads are heterogamous, some radiant heads may be heterogamous).

Phyllaries collectively constitute an involucre, usually number 5–21(–50+), usually are unequal (outermost usually shorter than the inner), and usually are arranged ± imbricately (overlapping like shingles) in 3–5(–15+), usually ± spiral series. Sometimes, the phyllaries are ± equal in 1–2 series; they are rarely wanting (e.g., Psilocarphus spp.). Phyllaries may be herbaceous or chartaceous to scarious and are often medially herbaceous with chartaceous to scarious borders and/or apices. The phyllaries “proper” are sometimes immediately subtended by a calyculus (pl. calyculi) of (1–)3–15+ distinct, usually shorter bractlets in 1(–3+) series (e.g., Coreopsis spp., Taraxacum spp.).

Receptacles may bear paleae (i.e., some or all florets are individually subtended by a bractlet called a palea or receptacular bract). Collectively paleae have been called “chaff” and paleate receptacles have been described as “chaffy.” Receptacles that bear paleae are referred to as paleate and receptacles that never bear paleae are referred to as epaleate. Epaleate receptacles sometimes bear subulate enations (e.g., some Gaillardia spp.) or bristles or subulate to linear scales (e.g., some Cynareae), or fine hairs (e.g., some Anthemideae). Epaleate receptacles (and paleate receptacles that have shed their paleae) may be smooth or pitted (alveolate, foveolate, etc.).

The terms tube, throat, and limb have been variously used in descriptions of corollas of composites. Here, in ± actinomorphic corollas of bisexual and functionally staminate disc florets, the tube is the part of the corolla proximal to the insertion of the staminal filaments, and the limb is the part that is distal to insertion of the filaments. The limb comprises, proximally, the throat and, distally, the lobes. The distinction between tube and throat hinges on insertion of filaments, not on external morphology.

The relatively flat portion of a corolla of a ligulate floret from a liguliflorous head (i.e., members of Cichorieae) is called a ligule; it terminates in 5 teeth or lobes. The relatively flat portion of a corolla of a ray floret is called a lamina; it terminates in 0–3(–4) teeth or lobes. More or less bilabiate corollas are characteristic of some members of Mutisieae and are seldom found in members of other tribes.

Fruits of composites have been called “achenes” because they resemble true achenes. Achenes are dry, hard, single-seeded fruits derived from unicarpellate, superior ovaries. Ovaries of composites are bicarpellate and inferior. Fruits derived from ovaries of composites are called cypselae (sing. cypsela, a term coined by C. de Mirbel in 1815). Morphology of an ovary of a composite at flowering is often markedly different from the morphology of the mature fruit (cypsela) derived from that ovary. References to cypselae in keys and descriptions here almost always refer to mature fruits, not to ovaries at flowering.

Shapes of cypselae have been used in distinguishing among species, genera, and even subtribes of composites. In most composites, cypselae are ± isodiametric in cross section. In some composites, cypselae are characteristically ± lenticular to elliptic in cross section. Such cypselae are said to be compressed (or laterally flattened) if the longer axis of the cross section is ± parallel to a radius of the head (e.g., Verbesina spp.). Cypselae are said to be obcompressed (or radially flattened) if the shorter axis of the cross section is ± parallel to a radius of the head (e.g., Coreopsis spp.).

In composites, pappi (sing. pappus) are found where calyces are usually found on inferior ovaries; pappi have been shown to be greatly modified calyces. They show a great range of diversity and are often diagnostic for recognition of taxa, especially at rank of genus and below. The forms of individual pappus elements intergrade. For keys and descriptions here, the following distinctions are made: cross sections of bristles and awns are ± circular or polygonal and have the longer diameter of the cross section no more than 3 times the shorter diameter. Pappus elements with “flatter” cross sections (i.e., longer diameter more than 3 times the shorter diameter) are called scales, regardless of relative overall lengths and widths of the elements. As used here, “subulate scale” and “setiform scale” mean much the same as “flattened bristle” of some authors. Pliable to stiff pappus bristles with diameters less than ca. 50 mm are called fine bristles; pliable to stiff bristles with diameters 50–100 mm are called coarse bristles. Rigid pappus elements with ± circular or polygonal cross sections greater than 100 mm in diameter are called awns. Bristles, awns, and scales may be smooth or finely to coarsely barbed or plumose. A scale of a pappus may terminate in one or more bristlelike or awnlike appendages; such scales are said to be aristate.

In keys and descriptions, “pappus” and “pappi” usually refer to structures found on cypselae (mature fruits), not to “immature pappi” of ovaries at flowering. Sometimes pappi of ovaries that do not form fruits (e.g., in functionally staminate florets of some tarweeds) may be taxonomically useful and may be referred to in descriptions and keys.

Following is a synoptic key to tribes into which genera of composites of the flora area are placed. Keys to genera within each tribe will be found in the accounts of the individual tribes. Because some traits in the key to tribes and in keys to genera within tribes may be difficult to assess, we have also provided a key to artificial groups of composites and keys to genera within those artificial groups. Those keys will be found following the key to tribes.

In the following key, “radiate heads” have ray florets; “eradiate heads” lack ray florets and may be disciform, discoid, or radiant. Ray florets have zygomorphic corollas with laminae; the laminae may be showy (as in some species of Helianthus) or inconspicuous (as in some species of Erigeron). Usually, we have included plants with inconspicuous ray laminae in keys to genera of both radiate and eradiate groups.

Some plants have questionably paleate or epaleate receptacles. Epaleate receptacles of some plants are notably pitted and have fimbriate to deeply lacerate pit borders; such receptacles have sometimes been interpreted as paleate. Plants with notably lacerate pit borders are usually keyed here as both paleate and epaleate.

Some plants with pappi of conspicuous bristles often have the bristles subtended by minute, inconspicuous scales. Although such plants technically belong to groups with pappi “wholly, or partially, of awns or scales,” they are usually also keyed here in groups characterized as having pappi “wholly of bristles,” because the scales are easily overlooked. As well, some pappus elements are borderline between being called subulate or setiform scales or being called “flattened bristles.” Consequently, some plants that technically belong to groups with pappi of scales are keyed both in groups with pappi “wholly of bristles” and in groups with pappi “wholly, or partially, of awns or scales.”

Tables

Table 1. Statistics for Volumes 19–21 of Flora of North America.

Tribe Total Genera Total Species Endemic Genera Endemic Species Introduced Genera Introduced Species Conservation Taxa
Volume 19
Mutisieae 7 14 1 4 0 0 0
Cynareae 17 116 0 48 14 50 30
Arctotideae 3 4 0 0 3 4 0
Vernonieae 6 25 1 18 2 2 0
Cichorieae 49 229 7 112 21 64 22
Calenduleae 4 7 0 0 4 7 0
Gnaphalieae 19 111 1 50 5 17 5
Inuleae 3 5 0 0 3 5 0
Plucheeae 3 12 0 3 0 3 0
Anthemideae 26 99 1 37 17 38 4
Volume 20
Astereae 77 719 33 561 1 5 175
Senecioneae 29 167 8 117 6 20 43
Volume 21
Heliantheae 148 746 40 470 6 22 131
Eupatorieae 27 159 5 98 0 3 16
Total for Asteraceae 418 2413 97 1518 82 240 426

Italic = introduced

References

Keys

Key to Tribes of Asteraceae

1 Heads liguliflorous (sap usually milky) Cichorieae
1 Heads disciform, discoid, radiate, radiant, or quasi-radiate, -radiant, or -liguliflorous (not truly liguliflorous; sap rarely milky) > 2
2 Anther bases usually rounded or obtuse to acute (sometimes sagittate, not tailed) > 3
2 Anther bases ± tailed > 9
3 Styles (in bisexual, fertile florets) usually distally dilated and ± cylindric, style branches linear (sometimes adhering almost to minutely parted tips or essentially lacking), style-branch appendages essentially 0 Arctotideae
3 Styles usually ± filiform (not distally dilated), style branches mostly lanceolate or linear (not adhering almost to tips), style-branch appendages mostly clavate, deltate, lanceolate, penicillate, or terete, sometimes filiform to linear, or essentially 0 > 4
4 Style-branch appendages usually terete to clavate (lengths usually 2–5+ times lengths of stigmatic lines; leaves usually opposite, sometimes whorled or alternate; heads discoid; corollas white, ochroleucous, or pink to purplish (not yellow) Eupatorieae
4 Style-branch appendages essentially 0 or ± penicillate or deltate to lanceolate, linear, or filiform (lengths mostly 0–3+ times lengths of stigmatic areas or lines) > 5
5 Margins of leaf blades usually 1–3-palmately or -pinnately divided (ultimate lobes usually linear to filiform), sometimes dentate or entire; phyllaries usually in 3–5+ series, unequal, and scarious or margins and/or apices notably scarious, sometimes in 1–2 series, subequal, and herbaceous, margins and apices little, if at all, scarious; pappi usually 0 (cypselar wall tissues sometimes produced as pappus-like, entire or toothed wings, coronas, or tubes), if pappi present, usually of scales, rarely of bristles Anthemideae
5 Margins of leaf blades entire, dentate, lobed, palmatifid, pinnatifid, or dissected (ultimate lobes sometimes linear to filiform); phyllaries in 1–2 series and ± equal to subequal or in 3–8+ series and unequal, usually herbaceous to chartaceous, sometimes scarious or with margins and/or apices notably scarious; pappi usually of scales and/or awns and/or bristles, sometimes 0 > 6
6 Heads usually discoid (quasi-radiant or quasi-radiate in Stokesia); corollas white, ochroleucous, or pink to cyanic (not yellow); style branches lance-linear to ± lanceolate, abaxially hirsutulous, adaxially stigmatic (continuously) from bases nearly to apices, appendages essentially 0 Vernonieae
6 Heads usually radiate or discoid, sometimes disciform, rarely ± radiant; corollas (some or all) usually yellow to orange, sometimes white, ochroleucous, or pink to cyanic, red, or purplish to brown; style branches ± linear to lanceolate, abaxially usually glabrous and smooth to papillate, sometimes hirsutulous, adaxially stigmatic (continuously or in 2 lines) from bases to appendages or apices, appendages usually penicillate or deltate to lanceolate, sometimes essentially 0 > 7
7 Leaves alternate; phyllaries in 1–2 series and equal to subequal in most spp. (sometimes coherent, often subtended by calyculi), rarely in 3+ series and unequal (e.g., Lepidospartum); receptacles epaleate; style-branch appendages usually penicillate or essentially 0; cypselae usually ± columnar to prismatic, seldom compressed, obcompressed, or flattened; pappi usually of (30–100+) fine (never plumose) bristles, rarely of subulate scales (e.g., Tetradymia spp.) or 0 Senecioneae
7 Leaves whorled, opposite, or alternate; phyllaries subequal in 1–2 series or un-equal in 3–5+ series; receptacles paleate or epaleate; style-branch appendages usually deltate to lanceolate, seldom penicillate; cypselae sometimes compressed, obcompressed, or flattened; pappi 0 or of scales and/or bristles and/or awns > 8
8 Leaves alternate (sometimes mostly basal); calyculi 0; phyllaries in 3–5+ series and unequal in most spp., in 1–2 series and subequal in some spp. (mostly linear to oblanceolate); receptacles usually epaleate (except Eastwoodia, Rigiopappus, and some Baccharis spp.); style-branch appendages glabrous adaxially; pappi (rarely 0) usually of bristles, sometimes of scales, rarely of awns 0 Astereae
8 Leaves usually wholly or partially opposite (at least proximally), sometimes mostly whorled or alternate (sometimes mostly basal); calyculi 0 or of 1–15+ bractlets; phyllaries usually in 3–5+ series and unequal (then usually lanceolate to ovate or broader), sometimes in 1–2 series and subequal (then usually linear to lanceolate); receptacles paleate or epaleate; style-branch appendages usually abaxially and adaxially papillate to hispidulous; pappi (sometimes 0) usually of scales (scales sometimes aristate, sometimes plumose), sometimes of awns or smooth, barbellulate to barbellate, or plumose bristles (e.g., Bebbia) Heliantheae
9 Corollas all 2-lipped Mutisieae (Acourtia, Trixis)
9 Corollas actinomorphic or zygomorphic (not all 2-lipped, usually none 2-lipped) > 10
10 Cypselae clavate (distally stipitate-glandular) Mutisieae (Adenocaulon)
10 Cypselae mostly columnar, ellipsoid, obpyramidal, or prismatic, seldom clavate (if clavate, not distally stipitate-glandular) > 11
11 Heads aggregated in second-order heads (florets usually 1–3 per individual head) > 12
11 Heads borne singly or in corymbiform, paniculiform, or racemiform arrays (not aggregated in second-order heads; florets usually 3–300+ per individual head) > 13
12 Shrubs (40–70 cm); cypselae glabrous or glabrate Mutisieae (Hecastocleis)
12 Perennials (100–200 cm); cypselae villous Cardueae (Echinops)
13 Heads homogamous (sometimes heterogamous and disciform or radiant, plants often prickly-spiny and thistlelike and/or phyllary apices spinose or ± expanded into distinct, often fimbriate-fringed, pectinate, and/or prickly appendages) Cardueae
13 Heads usually heterogamous (plants not prickly-spiny and thistlelike; sometimes homogamous and unisexual in Gnaphalieae; homogamous in Gochnatia of Mutisieae: shrubs with leaves abaxially white, tomentose, and adaxially green, glabrate or glabrous) > 14
14 Cypselae usually polymorphic within heads (straight, arcuate, contorted, or ± coiled), bodies usually tuberculate, ridged, and/or winged (blue- black and drupelike in Chrysanthemoides); pappi 0 Calenduleae
14 Cypselae usually monomorphic, bodies usually smooth or ribbed; pappi usually of bristles, sometimes of scales or 0 > 15
15 Heads radiate (ray corollas usually yellow) or quasi-radiate ("quasi-ray" corollas 2-lipped in Mutisieae) > 16
15 Heads usually disciform or discoid, rarely quasi-radiate (then "quasi-ray" corollas usually pink to purplish, sometimes whitish or ochroleucous, rarely yellowish; whitish corollas of peripheral pistillate florets in Sachsia of Plucheeae, sometimes with minute, 3-toothed laminae) > 17
16 Leaves basal and/or cauline (basal often withering before flowering); heads usually borne in corymbiform or paniculiform arrays, sometimes borne singly (stems ± leafy) Inuleae
16 Leaves all or mostly basal; heads mostly borne singly (stems scapiform) Mutisieae (Chaptalia, Leibnitzia)
17 Phyllaries usually (12–30+) in 3–10+ series (then scarious or margins and/or apices usually notably scarious), sometimes (3–10) in 1–2 series or 0 (plants often 1–10 cm and ± densely woolly) Gnaphalieae
17 Phyllaries (12–30+) in 3–6+ series (usually ± herbaceous to chartaceous, sometimes indurate, margins and/or apices seldom notably scarious) Plucheeae

Key to Artificial Groups of Genera of Asteraceae

1 Plants usually with milky sap; heads liguliflorous (corollas all ligulate, i.e., ± strap-shaped, 5-lobed) Group 1
1 Plants usually with clear sap, rarely with milky sap; heads discoid, disciform, radiant, or radiate (corollas of bisexual and/or functionally staminate florets mostly actinomorphic or nearly so) > 2
2 Ray corollas (or all corollas) ± 2-lipped (each with a 3-toothed, abaxial lamina oppo- site 2 curled, filiform to linear, adaxial lobes 1–3+ mm long) Group 2
2 Rays none or ray corollas not distinctly 2-lipped (ray corollas rarely with 1–2 teeth to 1+ mm opposite their laminae) > 3
3 Receptacles paleate (i.e., some or all inner florets each subtended by a palea, a receptacular bract) > 4
3 Receptacles epaleate (lacking paleae, sometimes bristly, setose, or hairy, or pitted and pit borders ± laciniate) > 9
4 Heads radiate (1 or more peripheral florets pistillate, neuter, or styliferous and sterile, their corollas zygomorphic; other florets bisexual or functionally staminate, their corollas actinomorphic or nearly so) > 5
4 Heads eradiate (corollas of all florets ± actinomorphic, sometimes corollas of outermost, peripheral florets with reduced or enlarged limbs, the heads discoid, disciform, or radiant) > 7
5 Pappi none or nearly so Group 3
5 Pappi of awns, bristles, and/or scales (on some or all ovaries or cypselae) > 6
6 Pappi wholly of bristles Acmella
6 Pappi wholly or partially of awns (the awns often barbed) and/or scales (the scales relatively broad to narrow, sometimes subulate to setiform, sometimes barbellate to plumose and/or distally aristate) Group 4
7 Pappi none or nearly so Group 5
7 Pappi of awns, bristles, and/or scales (on some or all ovaries or cypselae) > 8
8 Pappi wholly of bristles (the bristles smooth or barbellulate to plumose) Group 6
8 Pappi wholly or partially of awns (the awns often barbed) and/or scales (the scales relatively broad to narrow, sometimes subulate to setiform, sometimes barbellate to plumose and/or distally aristate) Group 7
9 Heads eradiate (corollas of all florets ± actinomorphic, sometimes corollas of outermost, peripheral florets with reduced or enlarged limbs, the heads discoid, disciform, or radiant) > 10
9 Heads radiate (1 or more peripheral florets pistillate, neuter, or styliferous and sterile, their corollas zygomorphic; other florets bisexual or functionally staminate, their corollas actinomorphic or nearly so) > 12
10 Pappi none or nearly so Group 12
10 Pappi of awns, bristles, and/or scales (on some or all ovaries or cypselae) > 11
11 Pappi wholly of bristles (the bristles smooth or barbellulate to plumose) Group 13
11 Pappi wholly or partially of awns (the awns often barbed) and/or scales (the scales relatively broad to narrow, sometimes subulate to setiform, sometimes barbellate to plumose and/or distally aristate) Group 14
12 Pappi none or nearly so Group 8
12 Pappi well-developed on some or all ovaries or cypselae > 13
13 Pappi wholly or partially of awns (the awns often barbed) and/or scales (the scales relatively broad to narrow, sometimes subulate to setiform, sometimes barbellate to plumose and/or distally aristate) Group 11
13 Pappi wholly of bristles (the bristles smooth or barbellulate to plumose) > 14
14 Ray corollas white, or pink to purple (with little, if any, yellow) Group 9
14 Ray corollas brown, orange, red, or yellow Group 10

Key to Genera of Group 2 "Ray" corollas or all corollas distinctly ± 2 lipped

1 Leaves: abaxial faces glabrous or with scattered, straight, sometimes glandular, hairs and/or double hairs > 2
1 Leaves: abaxial faces with dense, white or yellowish wool > 3
2 Perennials (caudices brown-woolly); corollas pink, lavender, or white Acourtia
2 Shrubs; corollas yellow Trixis
3 Heads chasmogamous, (produced well after rosette leaves); cypselae glabrous or with inflated, blunt hairs Chaptalia
3 Heads chasmogamous (early spring, before and concurrently with first rosette leaves) or cleistogamous (summer and fall); cypselae with slender, sharp-pointed hairs Leibnitzia

Key to Genera of Group 3 Heads radiate; receptacles paleate; pappi none or nearly so

1 Leaves alternate, margins of leaf blades usually 1–3-palmately or -pinnately lobed (ultimate lobes usually linear to filiform), sometimes dentate; phyllaries usually in 3–5+ series, unequal, scarious or margins and/or apices notably scarious > 2
1 Leaves mostly opposite, and/or sometimes alternate or whorled, margins of leaf blades usually entire, dentate, or lobed, sometimes 1–2-palmatifid or -pinnatifid (ultimate lobes sometimes linear to filiform); phyllaries usually in 3–5+ series and unequal, sometimes in 1–2 series and ± equal to subequal, usually herbaceous to chartaceous, sometimes with margins and/or apices notably scarious > 6
2 Heads in compact to open (± flat-topped), corymbiform or compound-corymbiform arrays; rays 3–5(–12); disc florets (5–)15–30+ (cypselae obcompressed) Achillea
2 Heads borne singly or in lax, corymbiform arrays; rays 5–30+; disc florets 40–300+ (cypselae mostly not, sometimes weakly, obcompressed) > 3
3 Disc corolla tubes ± cylindric (bases ± saccate or spurred, ± clasping apices of ovaries and/or cypselae); cypsela ribs or nerves (weak) 2 lateral and 1 adaxial > 4
3 Disc corolla tubes ± compressed or cylindric (bases sometimes proximally dilated, not saccate or spurred); cypsela ribs 9–10, or 0, or 2 lateral (sometimes ± winged) plus 3–10 finer ribs on each face > 5
4 Phyllaries 16–24 in 2–3+ series; rays orange, yellow, or white with yellow bases Cladanthus
4 Phyllaries 22–45+ in 3–4+ series; rays white Chamaemelum
5 Annuals (biennials); rays usually white, rarely yellow or pink Anthemis
5 Perennials; rays yellow Cota
6 Annuals; heads obscurely radiate (ray laminae minute; cypselae shed with 2 adjacent, ± fleshy paleae; Arizona) Parthenice
6 Annuals, biennials, perennials, subshrubs, or shrubs; heads usually conspicuously radiate (laminae showy; cypselae seldom shed with accessory structures) > 7
7 Plants often with tack-glands or pit-glands on stems, leaves, and/or phyllaries; phyllaries (or paleae functioning as phyllaries) usually in 1+ series (each often wholly or partly investing ovary of a subtended floret); paleae often in 1 series between ray and disc florets, often connate in a ring, sometimes each disc floret subtended by a palea; ray laminae often flabellate (lobe lengths often 1/2+ laminae) > 8
7 Plants without tack-glands or pit-glands; phyllaries in (1–)2–7+ series (seldom each inner phyllary wholly or partly investing ovary of a subtended floret); paleae seldom restricted to 1 series between ray and disc florets, all or nearly all disc florets subtended by paleae; ray laminae seldom flabellate (lobe lengths mostly 0–1/10 laminae) > 22
8 Ray cypselae obcompressed (each mostly or completely enveloped by a phyllary) > 9
8 Ray cypselae compressed, ± terete, ± 3-angled in cross section, or ± obcompressed (each ± 1/2 enveloped by a phyllary) > 13
9 Annuals, 1–20 cm; disc florets 1(–2) Hemizonella
9 Annuals or perennials, 2–150 cm; disc florets 3–120+ > 10
10 Perennials (rhizomatous); disc corollas white Holozonia
10 Annuals; disc corollas yellow (sometimes reddish with age) > 11
11 Disc pappi of 10, apically obtuse scales Achyrachaena
11 Disc pappi 0 > 12
12 Calyculi 0 or of 2–5 bractlets; ray florets 5; disc florets 6, function- ally staminate Lagophylla
12 Calyculi 0; ray florets 3–27; disc florets 4–120+, bisexual Layia
13 Annuals; styles of disc florets hairy proximal to minute branches (receptacles paleate throughout, ray corollas white with abaxial purple lines) Blepharipappus
13 Annuals, perennials, subshrubs, or shrubs; styles of disc florets glabrous proximal to branches > 14
14 Perennials (± scapiform; disc pappi of subulate, ciliate-plumose scales) Raillardella
14 Annuals, perennials (leafy-stemmed), subshrubs, or shrubs; disc pappi 0 or of scales, scales seldom both subulate and ciliate-plumose) > 15
15 Annuals or perennials; peduncle bracts without terminal pit-glands, tack-glands, or spines; rays yellow; ray cypselae usually compressed, rarely terete (cross sections usually ± 3-angled, then abaxial sides relatively broad, ± rounded, adaxial sides ± 2-faced, angles between those faces 15–70°; each ray cypsela usually completely or mostly enveloped by a phyllary) > 16
15 Annuals, subshrubs, or shrubs; peduncle bracts sometimes each with terminal pit-gland, tack-gland, or spine (or apiculus); rays yellow, whitish, or rose; ray cypselae terete to subterete or ± obcompressed (cross sections nearly circular with adaxial sides ± flattened to slightly bulging, or ± 3-angled, then abaxial sides usually ± broadly 2-faced, angles between those faces usually 90+° and adaxial sides ± flattened to slightly bulging; in Centromadia spp., distal leaves spine-tipped, each cypsela ± enveloped by a phyllary, cypselae sometimes compressed) > 17
16 Disc pappi 0 Madia
16 Disc pappi of 5–21 scales (scales sometimes subulate to setiform, bristlelike) Kyhosia
17 Annuals; leaves filiform to narrowly linear, margins often strongly revolute; peduncle bracts usually with tack-glands; ray corolla lobes (at least the lateral) often spreading (lengths often 1/2–5/6 of total laminae) > 18
17 Annuals, subshrubs, or shrubs; leaves linear or broader, margins seldom strongly revolute; peduncle bracts usually without tack-glands; ray corolla lobes ± parallel (lengths usually 1/10–1/2 of total laminae) > 19
18 Ray cypselae beaked; tack-glands absent Osmadenia
18 Ray cypselae not beaked; tack-glands present Calycadenia
19 Rays usually white, sometimes yellow, often with abaxial purple lines; cypselae not beaked or each with an inconspicuous, straight beak (beak lengths less than diams.) Hemizonia
19 Rays yellow (without abaxial purple lines); cypselae each with an adaxial, ascending beak (beak lengths greater than diams.) > 20
20 Peduncle bracts apiculate or each with apical spine Centromadia
20 Peduncle bracts not apiculate, without apical spines > 21
21 Annuals; peduncle bracts each with apical pit-gland; receptacles paleate throughout Holocarpha
21 Annuals, subshrubs, or shrubs; peduncle bracts without pit-glands; receptacle paleae usually restricted to bases of outermost disc florets (if in 2–3+ series, subshrubs or shrubs) Deinandra
22 Calyculi of 1–8+ bractlets > 23
22 Calyculi none > 28
23 Phyllaries connate 1/5–7/8+ their lengths Thelesperma
23 Phyllaries distinct to bases or nearly so > 24
24 Cypselae (at least inner) ± 4-angled, ± linear-fusiform, often apically attenuate or beaked (none winged) > 25
24 Cypselae all ± obcompressed > 26
25 Disc florets 10–20 (staminal filaments hairy near anthers); cypselae usually with 1 groove on each face Cosmos
25 Disc florets (5–)12–150+ (staminal filaments not hairy); cypselae with 0 or 2 grooves on each face Bidens
26 Rays 3–4 (laminae 1–2 mm); inner cypselae ± beaked Heterosperma
26 Rays usually 1, 2, 3, 5, 8, 13, 21+ (laminae mostly 4–30+ mm); cypselae not beaked > 27
27 Ray florets usually neuter or styliferous and sterile; cypsela wings membranous or corky, entire or irregularly thickened Coreopsis
27 Ray florets usually pistillate and fertile; cypsela wings ± corky, pectinately toothed Coreocarpus
28 Phyllaries (at least inner) usually falling with cypselae; ray florets pistillate, fertile > 29
28 Phyllaries persistent (in fruit); ray florets pistillate and fertile, or styliferous and sterile, or neuter > 33
29 Disc florets bisexual, fertile; anther thecae pale > 30
29 Disc florets usually functionally staminate (bisexual and fertile in Milleriinae, Guizotia); anther thecae dark (blackish to purplish) > 31
30 Phyllaries 10–20 in ± 2 series (outer 4 broadly lanceolate, foliaceous, nota- bly larger than inner) Tetragonotheca
30 Phyllaries 6–9 in 2 series, subequal or unequal (outer smaller than inner) Galinsoga
31 Rays 6–18 (corollas hairy at bases of tubes); disc florets bisexual, fertile. Guizotia
31 Rays 3–20+ (corollas seldom hairy at bases of tubes); disc florets functionally staminate > 32
32 Heads borne singly, usually pedunculate; fruits (perigynia) smooth or bullate to tuberculate (1–4 mm) Melampodium
32 Heads often in clusters of 2–3, mostly sessile; fruits ± prickly (4–8 mm) Acanthospermum
33 Receptacles spheric to high-conic or columnar (mostly 8–20+ mm) > 34
33 Receptacles mostly flat to convex or conic (mostly 0–5 mm) > 40
34 Phyllaries subequal or unequal (outer longer than inner); ray florets 3–21+, neuter; disc florets 100–200+, bisexual, fertile; stigmatic papillae usually in 2 lines > 35
34 Phyllaries subequal or unequal (outer usually shorter, rarely longer, than inner); ray florets 3–40+, usually pistillate and fertile, sometimes styliferous and sterile, or neuter; disc florets 4–200+, usually bisexual and fertile, sometimes functionally staminate; stigmatic papillae usually continuous, rarely in 2 lines > 36
35 Involucres (early flowering) hemispheric to rotate, 15–30+ mm diam.; phyllaries 15–30+ in 2–3 series, subequal; cypselae ± 4-angled, not strongly compressed, margins not pectinate or ciliate Rudbeckia
35 Involucres rotate, 8–12+ mm diam.; phyllaries 14–28+ in 2 series, unequal (outer notably longer than inner); cypselae strongly compressed, abaxial margin of each usually pectinate or ciliate Ratibida
36 Ray florets usually 5–21 (more in "double" cultivars), corollas usually yellow to orange, sometimes purple, red, or whitish (usually persistent, sessile, becoming papery) Zinnia
36 Ray florets usually (2–)5–35, corollas usually yellow to orange, sometimes white (seldom sessile, laminae usually borne on tubes, never persistent and becoming papery) > 37
37 Disc florets functionally staminate (only ray florets produce cypselae) > 38
37 Disc florets bisexual, fertile > 39
38 Phyllaries 8–10 in 2 series Lindheimera
38 Phyllaries 12–45+ in (2–)3–4 series Berlandiera
39 Leaves basal and cauline, alternate; involucres 12–40 mm diam.; rays dark purple to pale pink, white, or yellow Echinacea
39 Leaves cauline, opposite; involucres 10–15 mm diam.; rays yellow. Pascalia
40 Leaves mostly cauline and alternate (proximal sometimes opposite), or mostly opposite (distal sometimes alternate); ray florets usually neuter or styliferous and sterile > 41
40 Leaves usually cauline and opposite, sometimes mostly basal and/or mostly alternate; rays florets pistillate and fertile (if neuter, leaves mostly basal or alternate) > 47
41 Disc corollas yellow (bases often dilated, clasping tops of ovaries) Zaluzania
41 Disc corollas yellow to orange or brown-purple (bases not clasping tops of ovaries) > 42
42 Receptacle paleae each completely investing and falling with a cypsela (each forming a hardened perigynium) Sclerocarpus
42 Receptacle paleae sometimes conduplicate, ± enfolding cypselae (not forming perigynia) > 43
43 Heads borne singly (peduncles usually distally dilated, fistulose) Tithonia
43 Heads borne singly or in corymbiform, paniculiform, racemiform, or thyrsiform arrays (peduncles rarely, if ever, notably dilated or fistulose) > 44
44 Cypselae flattened, thin-margined Simsia
44 Cypselae ± compressed, biconvex, or 3- or 4-angled, often obpyramidal > 45
45 Shrubs (leaves often lobed, lobes usually 3–9, ± linear) Viguiera
45 Annuals or perennials (leaves not lobed) > 46
46 Annuals; leaf blades lanceolate to linear; involucres 5–6 mm diam.; phyllaries 11–17 Helianthus
46 Annuals or perennials; leaf blades lance-linear, lanceolate, ovate, rhombic, or rhombic-ovate; involucres 6–14 mm diam.; phyllaries 14–25 Heliomeris
47 Disc florets functionally staminate > 48
47 Disc florets bisexual and fertile > 52
48 Anther thecae green, staminal filaments hairy; Arizona Guardiola
48 Anther thecae dark or pale (not green), staminal filaments not hairy; e United States > 49
49 Ray florets 2–6, corollas pale yellow to whitish; disc florets 12–30+; cypselae (patently inserted on receptacles) 3–6-ribbed or -nerved (finely striate between ribs, apices often minutely beaked) Polymnia
49 Ray florets 7–13, corollas yellow; disc florets 40–80; cypselae (obliquely inserted on receptacles) 30–40-ribbed or -nerved (not beaked) > 50
50 Cypselae each shed separate from its subtending phyllary Smallanthus
50 Cypselae each enclosed within and shed within a perigynium (formed from an inner, subtending phyllary) > 51
51 Heads borne singly, usually pedunculate; fruits (perigynia) smooth or bullate to tuberculate (1–4 mm) Melampodium
51 Heads often in clusters of 2–3, mostly sessile; fruits ± prickly (4–8 mm) Acanthospermum
52 Stigmatic papillae in 2 lines > 53
52 Stigmatic papillae usually continuous, sometimes none (functionally staminate florets), rarely in 2 lines > 55
53 Leaf blades simple; heads borne singly; phyllaries ± connate, ± carinate Eriophyllum
53 Leaf blades 1–2-pinnately or -pedately lobed; heads in corymbiform to paniculiform arrays; phyllaries distinct, not carinate > 54
54 Leaves cauline, opposite; rays 5–8, pale yellow (fading white) Coreocarpus
54 Leaves mostly basal, alternate; rays 8, white Hymenopappus
55 Ray florets usually 5–21, corollas usually yellow to orange (usually persistent, sessile, becoming papery) Heliopsis
55 Ray florets (2–)5–35, corollas usually yellow to orange, sometimes white (seldom sessile, laminae usually borne on tubes, never persistent and becoming papery) > 56
56 Disc florets functionally staminate (only ray florets produce cypselae) > 57
56 Disc florets bisexual, fertile > 58
57 Phyllaries 8–10 in 2 series Chrysogonum
57 Phyllaries 12–45+ in (2–)3–4 series Silphium
58 Leaves mostly cauline, mostly opposite > 59
58 Leaves mostly basal, or basal and cauline, or cauline, mostly alternate > 63
59 Perennials (prostrate; cypselae often rostrate, each with apical boss or neck) Sphagneticola
59 Annuals or perennials (not prostrate; cypselae not rostrate) > 60
60 Cypselae 3–4-angled (weakly or not at all compressed or obcompressed, epidermes usually thick, corky) > 61
60 Cypselae (all or at least disc) strongly compressed or obcompressed or flattened (epidermes seldom thick and corky) > 62
61 Rays 20–40, white or whitish (paleae linear-filiform, not conduplicate) Eclipta
61 Rays 13–21, yellow to orange (paleae lanceolate to ovate, conduplicate) Pascalia
62 Perennials (coarse, 10–150 cm; larger leaves mostly 10–50 cm); involucres 10–50 mm diam.; phyllaries 22–32+ in ± 3 series Helianthella
62 Annuals or perennials (mostly 10–30+ cm; larger leaves mostly 2–10 cm); involucres 3–6+ mm diam.; phyllaries 8–15+ in 1–3 series Acmella
63 Cypselae prismatic, or nearly so, 3–4-angled > 64
63 Cypselae compressed to flattened > 67
64 Leaves mostly basal (cauline usually notably smaller than basal) Balsamorhiza
64 Leaves basal and cauline, or mostly cauline > 65
65 Leaves mostly cauline (blades narrowly oblong to linear, 5–25 mm wide) Scabrethia
65 Leaves basal and cauline, or mostly cauline (blades mostly 30–120 mm wide) > 66
66 Leaves mostly elliptic, lanceolate, or oblong (basal and cauline, basal usually notably larger than cauline, cauline mostly sessile) Wyethia
66 Leaves mostly orbiculate, ovate, or rounded-deltate (mostly cauline, mostly petiolate, proximal and distal usually ±similar) Agnorhiza
67 Cypselae winged Verbesina
67 Cypselae sometimes thin-edged (margins sometimes ciliate or corky-thickened, never truly winged) > 68
68 Perennials (scapiform); leaves all or mostly basal; involucres 20–30+ mm diam Enceliopsis
68 Perennials (rarely scapiform), subshrubs, or shrubs; leaves usually cauline, sometimes basal and cauline; involucres 4–30 mm diam > 69
69 Perennials (rhizomatous); leaves linear to filiform Phoebanthus
69 Perennials or shrubs (not rhizomatous); leaves mostly deltate, elliptic, lanceolate, or ovate (and most intermediate shapes, not linear to filiform) > 70
70 Ray florets 8–21, pistillate and fertile Helianthella
70 Ray florets 8–25(–40), neuter Encelia

Key to Genera of Group 4 Heads radiate; receptacles paleate; pappi wholly, or partially, of awns or scales

1 Plants often with tack-glands or pit-glands on stems, leaves, and/or phyllaries; phyllaries (or paleae functioning as phyllaries) usually in 1+ series (each often wholly or partly investing ovary of a subtended floret); paleae often in 1 series between ray and disc florets, often connate in a ring, sometimes each disc floret subtended by a palea; ray corolla laminae often flabellate (lobes often 1/2+ lengths of laminae; pappus scales often plumose and/or woolly) > 2
1 Plants without tack-glands or pit glands; phyllaries in (1–)2–7+ series (seldom each inner phyllary wholly or partly investing ovary of a subtended floret); paleae seldom restricted to 1 series between ray and disc florets, all or nearly all disc florets subtended by paleae; laminae of ray corollas seldom flabellate (lobes mostly 0–1/10 lengths of laminae); pappi usually of awns and/or scales (seldom plumose) > 16
2 Ray cypselae obcompressed (each mostly or completely enveloped by a phyllary) > 3
2 Ray cypselae compressed, ± terete, ± 3-angled in cross section, or ± obcompressed (each ± 1/2 enveloped by a phyllary) > 5
3 Perennials (rhizomatous); disc corollas white Holozonia
3 Annuals; disc corollas yellow (sometimes reddish with age) > 4
4 Pappi of apically obtuse scales Achyrachaena
4 Pappi of apically acute scales Layia
5 Annuals (styles of discs hairy proximal to minute branches; receptacles paleate throughout, ray corollas white with abaxial purple lines, pappi of subulate, plumose scales) Blepharipappus
5 Annuals, perennials, subshrubs, or shrubs (styles of discs glabrous proximal to branches) > 6
6 Perennials (± scapiform); disc pappi of subulate, ciliate-plumose scales Raillardella
6 Annuals, perennials (leafy-stemmed), subshrubs, or shrubs; disc pappi of scales (scales seldom both subulate and ciliate-plumose) > 7
7 Annuals or perennials; peduncle bracts without terminal pit-glands, tack-glands, or spines; ray corollas yellow; ray cypselae usually compressed, rarely terete (cross sections usually ± 3-angled, then abaxial sides relatively broad, ± rounded, adaxial sides ± 2-faced, angles between those faces 15–70°; each ray cypsela usually completely or mostly enveloped by a phyllary) > 8
7 Annuals, subshrubs, or shrubs; peduncle bracts sometimes each with terminal pit-gland, tack-gland, or spine (or apiculus); ray corollas yellow, whitish, or rose; ray cypselae terete to subterete or ± obcompressed (cross sections nearly circular with adaxial sides ± flattened to slightly bulging, or ± 3-angled, then abaxial sides usually ± broadly 2-faced, angles between those faces usually 90+° and adaxial sides ± flattened to slightly bulging; in Centromadia spp., distal leaves spine-tipped, each cypsela ± enveloped by a phyllary, cypselae sometimes compressed) > 12
8 Perennials > 9
8 Annuals > 10
9 Involucres campanulate to hemispheric; anthers ± dark purple; ray cypselae not beaked Kyhosia
9 Involucres campanulate, ellipsoid, or globose; anthers yellow to brownish; ray cypselae beaked Anisocarpus
10 Leaves all alternate, margins entire; heads borne singly; pappi of 3–5 scales Rigiopappus
10 Leaves: proximal opposite, distal alternate, margins entire or toothed; heads borne singly or in ± umbelliform or corymbiform arrays; pappi of 5–12 scales > 11
11 Anthers yellow to brownish Harmonia
11 Anthers ± dark purple Jensia
12 Annuals; leaves filiform to narrowly linear, margins often strongly revolute; peduncle bracts often with tack-glands; ray corolla lobes (at least the lateral) often spreading (lengths often 1/2–5/6 of total laminae) > 13
12 Annuals, subshrubs, or shrubs; leaves linear or broader, margins seldom strongly revolute; peduncle bracts usually without tack-glands; ray corolla lobes ± parallel (lengths usually 1/10–1/2 of total laminae) > 14
13 Ray cypselae beaked; tack-glands absent Osmadenia
13 Ray cypselae not beaked; tack-glands present Calycadenia
14 Rays usually white, sometimes yellow, often with abaxial purple lines; cypselae not beaked or each with an inconspicuous, straight beak (beak lengths less than diams.) Blepharizonia
14 Rays yellow (without abaxial purple lines); cypselae each with an adaxial, ascending beak (beak lengths greater than diams.) > 15
15 Peduncle bracts apiculate or each with an apical spine Centromadia
15 Peduncle bracts not apiculate, without apical spines Deinandra
16 Calyculi of 1–8+ bractlets > 17
16 Calyculi none > 24
17 Phyllaries (excluding calyculi) 3–4(–6) in 1(–2) series; disc florets 3–4+ (function- ally staminate) Dicranocarpus
17 Phyllaries (5–)8–34+ in ± 2 series; disc florets (5–)12–150+ > 18
18 Phyllaries connate 1/5–7/8+ their lengths Thelesperma
18 Phyllaries usually distinct, rarely connate ± 1/10 their lengths > 19
19 Cypselae (at least inner) ± 4-angled, ± linear-fusiform, often apically attenuate or beaked (none winged) > 20
19 Cypselae all ± obcompressed > 21
20 Disc florets 10–20 (staminal filaments hairy proximal to anther collars); cypselae usually with 1 groove on each face Cosmos
20 Disc florets (5–)12–150+ (staminal filaments not hairy); cypselae with 0 or 2 grooves on each face Bidens
21 Ray florets 3–4 (laminae 1–2 mm); inner cypselae ± beaked Heterosperma
21 Ray florets usually 1, 2, 3, 5, 8, 13, 21+ (laminae mostly 4–30+ mm); cypselae not beaked > 22
22 Cypselae rarely winged (margins sometimes thickened, winged in B. aristosa and B. polylepis); pappi of barbellate awns Bidens
22 Cypselae (some or all) usually ± winged; pappi of 2, bristly cusps or scales (in Coreopsis) or of 1–2 barbellate awns (in Coreocarpus) > 23
23 Ray florets usually neuter, or styliferous and sterile; wings of cypselae membranous or corky, entire or irregularly thickened. Coreopsis
23 Ray florets usually pistillate and fertile; wings of cypselae ± corky, pectinately toothed Coreocarpus
24 Phyllaries (at least inner) usually falling with cypselae; ray florets pistillate, fertile > 25
24 Phyllaries persistent (in fruit); ray florets pistillate and fertile, or styliferous and sterile, or neuter > 28
25 Disc florets usually functionally staminate; anther thecae dark (blackish to purplish; shoulders of cypselae may bear 1–3 pappus-like, triangular to ovate, or ± subulate enations; cypselae shed with subtending phyllary plus 2 contiguous discflorets and their investing paleae) Parthenium
25 Disc florets bisexual, fertile; anther thecae pale (cypselae sometimes shed with accessory structures) > 26
26 Phyllaries 10–20 in ± 2 series (outer 4 broadly lanceolate, foliaceous, notably larger than inner) Tetragonotheca
26 Phyllaries 6–30+ in 2–5 series (subequal or unequal, outer smaller than inner) > 27
27 Annuals (ray cypselae often each shed together with subtending phyllary and 2 adjacent paleae) Galinsoga
27 Perennials (cypselae shed separate from paleae) Tridax
28 Receptacles spheric to high-conic or columnar (mostly 8–20+ mm) > 29
28 Receptacles mostly flat to convex or conic (mostly 0–5 mm) > 36
29 Phyllaries subequal or unequal (outer longer than inner); ray florets 3–21+, neuter; disc florets 100–200+, bisexual, fertile; stigmatic papillae usually in 2 lines > 30
29 Phyllaries subequal or unequal (outer usually shorter, rarely longer, than inner); ray florets 3–40+, usually pistillate and fertile, sometimes styliferous and sterile, or neuter; disc florets 4–200+, usually bisexual and fertile, sometimes functionally staminate; stigmatic papillae usually continuous, rarely in 2 lines > 31
30 Involucres (early flowering) hemispheric to rotate, 15–30+ mm diam.; phyllaries 15–30+ in 2–3 series, subequal; cypselae ± 4-angled, not strongly compressed, margins not pectinate or ciliate Rudbeckia
30 Involucres rotate, 8–12+ mm diam.; phyllaries 14–28+ in 2 series, unequal (outer notably longer than inner); cypselae strongly compressed, abaxial margin of each usually pectinate or ciliate Ratibida
31 Anther thecae pale; stigmatic papillae in 2 lines Amblyolepis
31 Anther thecae usually dark; stigmatic papillae usually continuous, rarely in 2 lines > 32
32 Ray florets usually 5–21 (more in "double" cultivars), corollas usually yellow to orange, sometimes purple, red, or whitish (usually persistent, sessile, becoming papery) Zinnia
32 Ray florets usually (2–)5–35, corollas usually yellow to orange, sometimes white (seldom sessile, laminae usually borne on tubes, never persistent and becoming papery) > 33
33 Disc florets functionally staminate (only ray florets produce cypselae) > 34
33 Disc florets bisexual, fertile > 35
34 Phyllaries 8–10 in 2 series Lindheimera
34 Phyllaries 12–45+ in (2–)3–4 series Berlandiera
35 Leaves basal and cauline, alternate; involucres 12–40 mm diam.; rays dark purple to pale pink, white, or yellow Echinacea
35 Leaves cauline, opposite; involucres 10–15 mm diam.; rays yellow Pascalia
36 Leaves mostly cauline and alternate (proximal sometimes opposite), or mostly opposite (distal sometimes alternate); ray florets usually neuter or styliferous and sterile; pappi usually fragile or readily falling, sometimes persistent, of scales or awns > 37
36 Leaves usually cauline and opposite, sometimes mostly basal and/or mostly alternate; ray florets pistillate and fertile (if neuter, leaves mostly basal or alternate); pappi usually persistent, of awns, bristles, and/or scales > 44
37 Receptacle paleae each completely investing and falling with cypsela (each forming a hardened perigynium) Sclerocarpus
37 Receptacle paleae sometimes conduplicate, ± enfolding cypselae (not forming perigynia) > 38
38 Heads borne singly (peduncles usually distally dilated, fistulose) Tithonia
38 Heads borne singly or in corymbiform, paniculiform, racemiform, or thyrsiform arrays (peduncles rarely, if ever, notably dilated or fistulose) > 39
39 Cypselae flattened, thin-margined Simsia
39 Cypselae ± compressed, biconvex, or 3- or 4-angled, often obpyramidal > 40
40 Cypselae glabrous or glabrate > 41
40 Cypselae usually ± strigose, sometimes glabrous or glabrate (pappi of 2–6+ persistent, readily falling, or tardily falling, scales) > 42
41 Shrubs (leaves often lobed, lobes usually 3–9, ± linear) Viguiera
41 Annuals or perennials (leaves not lobed) Helianthus
42 Shrubs; involucres 5–9 mm diam Bahiopsis
42 Annuals or perennials; involucres (5–)7–40+ mm diam > 43
43 Pappi readily falling Helianthus
43 Pappi persistent or tardily falling Viguiera
44 Stigmatic papillae in 2 lines > 45
44 Stimatic papillae usually continuous, sometimes none, rarely in 2 lines > 49
45 Pappi of 1–2 retrorsely barbellate awns Coreocarpus
45 Pappi of 2–50 smooth to barbellate scales > 46
46 Disc cypselae 4–5-angled > 47
46 Disc cypselae not angled > 48
47 Leaves mostly basal or basal and cauline, alternate, margins usually 1–2-pinnately or -palmati-pinnately lobed; phyllaries distinct Hymenopappus
47 Leaves mostly cauline, mostly alternate (proximal sometimes opposite), margins entire or toothed; phyllaries ± connate Eriophyllum
48 Rays 2–4; pappi of ca. 50, setiform scales Pseudoclappia
48 Rays 5–15+; pappi of 6–10+ scales Gaillardia
49 Ray florets usually 5–21, corollas usually yellow to orange, sometimes purple, red, or whitish (usually persistent, sessile, becoming papery) > 50
49 Ray florets usually (2–)5–35, corollas usually yellow to orange, sometimes white (seldom sessile, laminae usually borne on tubes, never persistent and becoming papery) > 51
50 Leaf margins serrate to coarsely toothed Heliopsis
50 Leaf margins entire Sanvitalia
51 Disc florets functionally staminate (only ray florets produce cypselae) > 52
51 Disc florets bisexual, fertile > 54
52 Phyllaries 8–10 in 2 series Chrysogonum
52 Phyllaries 12–45+ in (2–)3–4 series > 53
53 Ray florets 8–35 (in 1–3 series); cypselae shed alone without accessory struc- tures Silphium
53 Ray florets usually (2–)8(–13); cypselae each shed together with subtending phyllary and 2–4 adjacent paleae and disc florets Engelmannia
54 Leaves mostly basal, or basal and cauline, or cauline, mostly alternate > 55
54 Leaves mostly cauline, mostly opposite > 64
55 Cypselae prismatic, or nearly so, 3–4-angled > 56
55 Cypselae compressed to flattened > 58
56 Leaves mostly cauline (blades narrowly oblong to linear, 5–25 mm wide) Scabrethia
56 Leaves basal and cauline, or mostly cauline (blades mostly 30–120 mm wide) > 57
57 Leaves mostly elliptic, lanceolate, or oblong (basal and cauline, basal usually notably larger than cauline, cauline mostly sessile) Wyethia
57 Leaves mostly orbiculate, ovate, or rounded-deltate (mostly cauline, mostly petiolate, proximal and distal usually ± similar) Agnorhiza
58 Cypselae winged; pappi persistent, of 2(–3) scales (scales often aristate or subulate, without additional scales) Verbesina
58 Cypselae sometimes thin-edged (margins sometimes ciliate or corky-thickened, never truly winged); pappi usually of (1–)2 subulate scales or bristlelike awns plus 2–4+ shorter scales (rarely of 2–3 aristate scales without additional scales) > 59
59 Perennials (scapiform); leaves all or mostly basal; involucres 20–30+ mm diam Enceliopsis
59 Perennials (rarely scapiform), subshrubs, or shrubs; leaves usually cauline, sometimes basal and cauline; involucres 4–30 mm diam > 60
60 Perennials (rhizomatous); leaves linear to filiform Phoebanthus
60 Perennials or shrubs (not rhizomatous); leaves mostly deltate, elliptic, lanceolate, or ovate (and most intermediate shapes, not linear to filiform) > 61
61 Ray florets 8–21, pistillate and fertile Helianthella
61 Ray florets 8–40, neuter, or styliferous and sterile > 62
62 Subshrubs or shrubs (glabrous or ± scabrellous, usually vernicose); phyllaries 12–40 in 2–4+ series (subequal or unequal, outer longer) Flourensia
62 Annuals, perennials, or shrubs (glabrous or canescent, hirtellous, scabrellous, strigose, or tomentose, often gland-dotted or glandular-puberulent to stipitate-glandular, seldom vernicose); phyllaries 18–30(–50+) in 2–3+ series (subequal or unequal, outer shorter) > 63
63 Perennials (E. nutans), subshrubs, or shrubs; pappi sometimes fragile, of 2 weak, villous scales. Encelia
63 Annuals or perennials; pappi usually persistent, of 2 subulate scales Geraea
64 Pappi usually coroniform or cyathiform (cypselae often rostrate, each with apical boss or neck) > 65
64 Pappi usually of 2–4+ awns, bristles, and/or scales (not cyathiform, cypselae not rostrate) > 66
65 Subshrubs or shrubs (erect); cypselae (some or all) strongly compressed, notably winged Wedelia
65 Perennials (prostrate); cypselae strongly biconvex to plumply 3–4-angled (not compressed, not winged, epidermes usually corky, often tuberculate) Sphagneticola
66 Some or all cypselae winged (each bordered by wing of membranous or corky tissue different from that of body of cypsela) > 67
66 Cypselae sometimes sharp-edged (not winged) > 69
67 Heads in glomerules or borne singly (sessile or subsessile in axils); cypselae winged (rays, not discs, wings lacerate) Synedrella
67 Heads borne singly or in corymbiform, dichasiiform, or paniculiform arrays (not sessile); cypselae winged (rays and discs, wings not lacerate) > 68
68 Phyllaries 9–30 in 1–4 series (outer 2–5 similar to others, unlike foliage); pappi of 2(–3) persistent (often aristate or subulate) scales without addi- tional scales Verbesina
68 Phyllaries 26–38+ in 3–4+ series (outer 2–6+ similar to foliage in shape, texture, and indument); pappi of 2–3 fragile or persistent awns or subulate scales plus 2–8+ distinct or basally connate, erose or lacerate scales (often each cypsela with additional seta on inner shoulder) Jefea
69 Cypselae 3–4-angled (weakly or not at all compressed or obcompressed, epidermes usually thick, corky) > 70
69 Cypselae (all or at least disc) strongly compressed or obcompressed or flattened (epidermes seldom thick and corky) > 72
70 Rays 20–40, white or whitish (paleae linear-filiform, not conduplicate) Eclipta
70 Rays 7–30, yellow to orange (paleae lanceolate to ovate, conduplicate) > 71
71 Leaves elliptic, linear, oblanceolate, obovate, or ovate, glabrous or puberulent to villous and/or sericeous (outer phyllaries elliptic, oblan- ceolate, or ovate) Borrichia
71 Leaves lanceolate to lance-linear, sparsely scabrous (outer phyllaries lance-linear to linear) Pascalia
72 Annuals or perennials (mostly 5–30+ cm; larger leaves mostly 1–5+ cm); involucres 3–8 mm diam.; phyllaries 5 in 1(–2) series Calyptocarpus
72 Perennials (coarse, 10–150 cm; larger leaves mostly 5–50 cm); involucres 10–50 mm diam.; phyllaries 12–35 in 2–5 series > 73
73 Leaf blades oblanceolate to lanceolate or lance-linear (longer usually 8–50 cm), margins entire Helianthella
73 Leaf blades rounded-deltate to ovate or lance-ovate (longer usually 5– 8 cm), margins coarsely serrate Lasianthaea

Key to Genera of Group 5 Heads eradiate; receptacles paleate; pappi none or nearly so

1 Leaves mostly opposite (distal sometimes alternate; sometimes whorled) > 2
1 Leaves mostly alternate (proximal sometimes opposite) > 17
2 Phyllaries absent ("involucre" sometimes consisting of 1 series of paleae) > 3
2 Phyllaries present > 4
3 Receptacles ± obovoid; disc florets functionally staminate Psilocarphus
3 Receptacles flat or convex; disc florets bisexual {corollas yellow to red-orange, some times purplish) Madia
4 Heads bisexual or unisexual; anthers distinct > 5
4 Heads bisexual; anthers connate > 9
5 Pistillate and functionally staminate florets in separate heads (cypselae shed within hardened, often prickly, spiny, tuberculate, or winged, perigynia, forming "burs" or nutlike structures) > 6
5 Pistillate and functionally staminate florets usually together in same heads (sometimes some heads staminate; cypselae not enclosed within perigynia) > 7
6 Staminate heads: phyllaries partially or wholly connate; receptacles ± flat or convex; pistillate heads: phyllaries 12–30(–80+) in 1–8+ series, outer (1–)5–8 distinct or ± connate, the rest ± connate (becoming indurate, their distinct tips forming straight or hooked spines, tubercles, or wings). Ambrosia
6 Staminate heads: phyllaries distinct to bases; receptacles conic to columnar; pistillate heads: phyllaries 30–75+ in 6–12+ series, outer 5–8 distinct, the rest proximally connate (becoming indurate, their distinct tips usually forming hooked spines) Xanthium
7 Cypselae strongly obcompressed to -obflattened (subtended by accrescent phyllaries, margins corky-winged and ± irregularly toothed) Dicoria
7 Cypselae sometimes ± obcompressed (not subtended by accrescent phyllaries, margins not corky-winged and toothed) > 8
8 Heads in (bracteate) racemiform or spiciform arrays Iva
8 Heads in (± ebracteate) paniculiform arrays Cyclachaena
9 Corollas white or pinkish (phyllaries 10–15+, prominently 2–3-nerved) Isocarpha
9 Corollas usually yellow to orange or ochroleucous, sometimes whitish > 10
10 Calyculi present > 11
10 Calyculi absent > 13
11 Calyculi of (3–)5–13(–21+), ± herbaceous (sometimes foliaceous) bractlets or bracts (sometimes surpassing phyllaries); cypselae rarely winged Bidens
11 Calyculi usually of 1–8+ bractlets; capselae often winged > 12
12 Calyculi of 1–3+ bractlets; phyllaries usually distinct, rarely connate ± 1/10 their lengths Coreocarpus
12 Calyculi of 3–8+ bractlets; phyllaries connate 1/5–7/8+ their lengths Thelesperma
13 Disc florets functionally staminate (e United States) Polymnia
13 Disc florets bisexual, fertile > 14
14 Shrubs; phyllaries in ± 1 series, proximally connate (heads with 1– 2 flowers, borne in headlike glomerules) Lagascea
14 Annuals, perennials, or subshrubs; phyllaries in (1–)2–5 series, distinct or inner ± connate > 15
15 Phyllaries in ± 2 series, ± equal Coreocarpus
15 Phyllaries in 1–5 series, subequal or unequal > 16
16 Receptacles flat to convex or ± conic; cypselae usually winged Verbesina
16 Receptacles conic; cypselae not winged Acmella
17 Annuals; involucres absent, vestigial, or inconspicuous, often simulated by leaves or paleae, sometimes glandular > 18
17 Annuals, biennials, perennials, subshrubs, or shrubs; involucres present > 26
18 Stems and leaves villous to hispid, glandular-pubescent distally Madia
18 Stems and leaves usually arachnoid-sericeous to lanuginose, sometimes glabrescent, usually eglandular > 19
19 Bisexual florets (1–)2–10(–11), pappi of (11–)13–28+ bristles visible in heads; functionally staminate florets 0 > 20
19 Bisexual florets 0 or 2–7, pappi 0; functionally staminate florets 0 or 2–12, pappi 0, or of 1–10(–13) bristles hidden in heads > 21
20 Receptacles fungiform to obovoid (heights 0.4–1.6 times diams.); most pistillate paleae ± saccate, each ± enclosing a floret, apices blunt; innermost paleae spreading in fruit; cypselae dimorphic (outer longer than inner) Logfia
20 Receptacles cylindric to clavate (heights 5–15 times diams.); most pistillate paleae open to ± folded (at most, each enfolding, not enclosing, a floret; apices acuminate to aristate); innermost paleae erect to ascending in fruit; cypselae monomorphic (outer ± equaling inner) Filago
21 Pistillate paleae saccate most of lengths (each enclosing a floret, outermost rarely open); pappi 0, or of 1–10(–13) bristles > 22
21 Pistillate paleae open most of lengths, flat or concave to loosely folded (not enclosing florets); pappi 0 > 24
22 Staminate paleae 5(–7), ± spreading proximally, enlarged in fruit (apices incurved to uncinate); pistillate paleae with 3, ± parallel (promi- nent) nerves; cypselae: corolla scars apical Ancistrocarphus
22 Staminate paleae 0, or 1–4, erect, not enlarged in fruit (apices erect); pistillate paleae with 5+, reticulate (and prominent) or ± parallel (and obscure) nerves; cypselae: corolla scars subapical to ± lateral > 23
23 Pistillate paleae (obcompressed to terete, not galeate): wings ± erect (and apical); receptacles cylindric to clavate (heights 2.8–8 times diams.); phyllaries 0 or 1–4 (similar to paleae); cypselae: corolla scars subapical Stylocline
23 Pistillate paleae (compressed, galeate): wings ± erect (and lateral) or inflexed (and subapical); receptacles depressed-spheric to obovoid (heights 0.5–1.8 times diams.); phyllaries 4–6 (unlike paleae); cypselae: corolla scars ± lateral Micropus
24 Bisexual paleae saccate, each enclosing a floret, apices 2-fid or 3-fid; cypselae (at least outer) strigose; coastal Texas Micropsis
24 Bisexual or staminate paleae flat to concave, not enclosing florets, apices entire; cypselae glabrous; c, w North America > 25
25 Receptacles glabrous; pistillate paleae falling (all or the inner together); staminate (or bisexual) paleae: bodies ± spatulate (apices scarcely enlarged); c North America Diaperia
25 Receptacles bristly; pistillate paleae persistent; staminate paleae: bodies obovate (apices enlarged); California, Oregon Hesperevax
26 Plants usually aromatic; phyllary margins and apices scarious > 27
26 Plants usually not aromatic; phyllary margins and apices herbaceous > 29
27 Heads in broad, paniculiform arrays, or in narrow, racemiform or spiciform arrays; disc florets 2–20(–30+) Artemisia
27 Heads borne singly or in lax, corymbiform arrays; disc florets 60–250+ > 28
28 Perennials; stems villous to strigoso-sericeous; leaf blades 2–3-pinnately lobed Chamaemelum
28 Subshrubs; stems often tomentose to lanate, sometimes glabrate or glabrous and gland-dotted; leaf blades 1-pinnately lobed (± vermiform) Santolina
29 Disc florets bisexual, fertile > 30
29 Disc florets pistillate and functionally staminate (sometimes in separate, unisexual heads) > 33
30 Subshrubs; leaf blades linear to filiform; involucres obconic Varilla
30 Annuals, perennials, subshrubs, or shrubs; leaf blades suborbiculate, deltate, ovate, cordate-ovate, elliptic, lanceolate, linear, oblanceolate, rhombic, or spatulate; involucres turbinate, campanulate, hemispheric, or broader > 31
31 Cypselae prismatic, or nearly so, 3–4-angled Agnorhiza
31 Cypselae compressed to flattened > 32
32 Annuals or perennials; cypselae winged Verbesina
32 Perennials, subshrubs, or shrubs; cypselae sometimes thin-edged (margins ciliate, never winged) Encelia
33 Pistillate and functionally staminate florets in separate heads (cypselae shed within hardened, often prickly, spiny, tuberculate, or winged, perigynia, forming "burs" or nutlike structures) > 34
33 Pistillate and functionally staminate florets usually together in same heads (sometimes some heads staminate; cypselae not enclosed within perigynia) > 35
34 Staminate heads: phyllaries partially or wholly connate; receptacles ± flat or convex; pistillate heads: phyllaries 12–30(–80+) in 1–8+ series, outer (1–)5–8 distinct or ± connate, the rest ± connate (becoming indurate, their distinct tips forming straight or hooked spines, tubercles, or wings) Ambrosia
34 Staminate heads: phyllaries distinct to bases; receptacles conic to columnar; pistillate heads: phyllaries 30–75+ in 6–12+ series, outer 5–8 distinct, the rest proximally connate (becoming indurate, their distinct tips usually forming hooked spines) Xanthium
35 Cypselae shed with accessory structures (each with at least 2 paleae, sometimes florets and/or a phyllary as well); anthers ± connate Parthenium
35 Cypselae usually shed free of accessory structures; anthers weakly coherent or distinct > 36
36 Subshrubs or shrubs (phyllaries, paleae, and cypselae ± villous) Oxytenia
36 Annuals or perennials (rarely woody at bases; phyllaries, paleae, and cypselae glabrous or strigillose and/or hispidulous) > 37
37 Heads usually in loose, (± bracteate or ebracteate) paniculiform arrays (sometimes 3–6+ distal to axil of each bract); herbaceous phyllaries usually 5; lobes of functionally staminate corollas soon reflexed Hedosyne
37 Heads mostly borne singly (in leaf axils or remote from axils, ± scattered); herbaceous phyllaries usually 3+; lobes of functionally staminate corollas usually erect at flowering Chorisiva

Key to Genera of Group 6 Heads eradiate; receptacles paleate; pappi wholly of bristles

1 Leaves all or mostly opposite > 2
1 Leaves alternate > 4
2 Involucres cylindric; corollas white or purple to blue, lavender, or reddish Chromolaena
2 Involucres ± hemispheric or broader to ovoid; corollas yellow to orange (lobes sometimes reddish) > 3
3 Involucres ± hemispheric or broader; receptacles flat to convex; corolla throats narrowly funnelform to cylindric; cypselae obpyramidal; pappi of 2–12 barbellulate bristles Melanthera
3 Involucres ± hemispheric to ovoid; receptacles conic; corolla throats campanulate; cypselae ellipsoid or obovoid; pappi of 1–3 awnlike bristles Acmella
4 Annuals; involucres 0 or inconspicuous > 5
4 Perennials, subshrubs, or shrubs; involucres conspicuous > 8
5 Bisexual florets 0; functionally staminate florets 2–6, pappi (0–)1–10(–13) bristles (hidden in heads) > 6
5 Bisexual florets (1–)2–10(–11), pappi of (11–)13–28+ bristles visible in heads; functionally staminate florets 0 > 7
6 Pistillate paleae (obcompressed to terete, not galeate): wings ± erect (and apical); receptacles cylindric to clavate (heights 2.8–8 times diams.); phyllaries 0 or 1–4 (similar to paleae); cypselae: corolla scars subapical Stylocline
6 Pistillate paleae (compressed, galeate): wings ± erect (and lateral) or inflexed (and subapical); receptacles depressed-spheric to obovoid (heights 0.5–1.8 times diams.); phyllaries 4–6 (unlike paleae); cypselae: corolla scars ± lateral Micropus
7 Receptacles fungiform to obovoid (heights 0.4–1.6 times diams.); most pistillate paleae ± saccate, each ± enclosing a floret, apices blunt; innermost paleae spreading in fruit; cypselae dimorphic (outer longer than inner) Logfia
7 Receptacles cylindric to clavate (heights 5–15 times diams.); most pistillate paleae open to ± folded (at most, each enfolding, not enclosing a floret; apices acuminate to aristate); innermost paleae erect to ascending in fruit; cypselae monomorphic (outer ± equaling inner) Filago
8 Subshrubs or shrubs Lorandersonia
8 Perennials > 9
9 Phyllary tips spiny or hooked-spiny > 10
9 Phyllary tips not spiny or hooked-spiny > 11
10 Leaf margins spiny; phyllary tips spiny Carlina
10 Leaf margins not spiny; phyllary tips hooked-spiny Arctium
11 Corollas yellow Agnorhiza
11 Corollas white, pinkish, lavender to dark magenta, pinkish purple, or ± blue > 12
12 Cypselae 5-angled or -grooved; pappi of 1(–5+), ± glandular setae Hartwrightia
12 Cypselae ca. 10-ribbed; pappi of 35–40 barbellulate to barbellate bristles Carphephorus

Key to Genera of Group 7 Heads eradiate; receptacles paleate; pappi wholly, or partially, of awns or scales

1 Florets 1(–2) per head (heads in globose, second-order heads or headlike glomerules) > 2
1 Florets (5–)20–800+ per head (heads borne singly or in arrays, not in globose, second-order heads or headlike glomerules) > 3
2 Leaf margins spiny (plants thistlelike) Echinops
2 Leaf margins ± serrate (not spiny, plants not thistlelike) Lagascea
3 Phyllaries 0 (outer receptacle paleae forming an "involucre"; inner paleae 0 or each subtending a floret) > 4
3 Phyllaries in (1–)2–7+ series (seldom each phyllary wholly or partly investing ovary of a subtended floret; receptacle paleae usually each subtending a floret) > 6
4 Annuals (inner receptacle paleae falling, distinct, each subtending a floret) Layia
4 Perennials (inner receptacle paleae 0) > 5
5 Leaves mostly basal (in rosettes), opposite, faces sericeous Raillardella
5 Leaves basal and cauline, proximal opposite, distal alternate, faces hirsute to strigose or pubescent Anisocarpus
6 Calyculi of (0–)1–21+ bractlets or bracts (sometimes surpassing phyllaries); phyllaries usually in ± 2 series, usually ± equal; disc cypselae ± obcompressed to flat (often winged), or ± unequally 3–4-angled and linear-fusiform (pappi of 1–2 usually retrorsely, sometimes antrorsely, barbellate or ciliate, rarely smooth, subulate scales or awns) > 7
6 Calyculi 0; phyllaries in 1–7+ series; disc cypselae seldom obcompressed or 4-angled and linear-fusiform (usually not winged) > 9
7 Phyllaries connate 1/5–7/8+ their lengths Thelesperma
7 Phyllaries usually distinct, rarely connate ± 1/10 their lengths > 8
8 Cypselae (some or all) usually ± winged; pappi of 1–2 barbellate awns Coreocarpus
8 Cypselae rarely winged; pappi usually of (1–)2–4(–8) usually barbellate or ciliate, rarely smooth, awns Bidens
9 Phyllaries falling together with cypselae (plus 2 contiguous disc florets and their invest- ing paleae) Parthenium
9 Phyllaries persistent (in fruit) > 10
10 Receptacles columnar Rudbeckia
10 Receptacles mostly flat to convex or conic > 11
11 Leaves basal and cauline, mostly alternate; pappi usually fragile or readily falling Hartwrightia
11 Leaves usually cauline and opposite, sometimes mostly basal and/or mostly alternate; pappi usually persistent (readily falling in Melanthera) > 12
12 Disc corollas lavender, pink, purple, or white; anther thecae cream or purple Marshallia
12 Disc corollas usually orange to yellow, sometimes brown, pink, purple, red, or white; anther thecae pale or dark (not violet) > 13
13 Stigmatic papillae in 2 lines > 14
13 Stigmatic papillae usually continuous, sometimes none (functionally staminate florets), rarely in 2 lines > 17
14 Paleae conduplicate (each ± clasping a cypsela) > 15
14 Paleae subulate or setiform (not conduplicate and each clasping a cypsela) > 16
15 Pappi of 5–8 linear-lanceolate, erose-margined scales. Eastwoodia
15 Pappi of 15–25+ plumose, setiform scales Bebbia
16 Corollas white, pinkish, cream, or yellow; cypselae clavate to ± cylindric or compressed, obscurely 8–20-angled; pappi of (1–)4–20, ± erose scales in 1–4 series Chaenactis
16 Corollas yellow or orange to red, purplish, or brown; cypselae obpyramidal to clavate, ± 4-angled; pappi of 6–10+ medially thickened, laterally scarious scales in 1–2 series (all, some, or none aristate) Gaillardia
17 Leaves mostly cauline, mostly opposite > 18
17 Leaves mostly basal, or basal and cauline, or cauline, mostly alternate > 20
18 Corollas white or whitish; pappi readily falling, of 2–12 barbellate awns (or bristles) Melanthera
18 Corollas yellow to orange; pappi usually persistent and coroniform or cyathiform (each an erose, fimbriate, or lacerate cup, with or without additional awns or bristles, borne on rostra), or of 2–4+ awns and/or scales > 19
19 Pappi usually of 2–3 (often aristate or subulate) scales (not cyathiform; cypselae not rostrate) Verbesina
19 Pappi usually cyathiform (fimbriate cups plus 0–3 coarse bristles or awns, borne on rostra; cypselae often rostrate). Wedelia
20 Cypselae winged; pappi of 2(–3) scales (scales often aristate or subulate, without additional scales) Verbesina
20 Cypselae sometimes thin-edged (margins sometimes ciliate or corky-thickened, never truly winged); pappi usually of (1–)2, subulate scales or bristlelike awns plus 2–4+ shorter scales (rarely of 2–3, aristate scales without additional scales) > 21
21 Subshrubs or shrubs (glabrous or ± scabrellous, usually vernicose); phyllaries 12–40 in 2– 4+ series (subequal or unequal, outer longer) Flourensia
21 Annuals, perennials, or shrubs (glabrous or canescent, hirtellous, scabrellous, strigose, or tomentose, often gland-dotted or glandular-puberulent to stipitate-glandular, seldom vernicose); phyllaries 18–30(–-50+) in 2–3+ series (subequal or unequal, outer shorter) > 22
22 Perennials (E. nutans), subshrubs, or shrubs; pappi sometimes fragile, of 2 weak, bristlelike (villous) scales Encelia
22 Annuals or perennials; pappi usually persistent, of 2 awns or subulate scales Geraea

Key to Genera of Group 8 Heads radiate; receptacles epaleate; pappi none or nearly so

1 Cypselae usually polymorphic within heads (straight, arcuate, contorted, or ± coiled), sometimes ± beaked (bodies usually tuberculate, ridged, and/or winged, sometimes drupelike) > 2
1 Cypselae usually monomorphic, sometimes dimorphic, within heads, rarely, if ever, beaked (bodies smooth, papillate, muricate, ribbed, nerved, or rugulose, sometimes winged) > 5
2 Shrubs or trees; cypselae fleshy (drupelike) Chrysanthemoides
2 Annuals, perennials, or shrubs; cypselae not fleshy (often tuberculate or ridged and/or winged) > 3
3 Disc florets bisexual (some or all fertile) Dimorphotheca
3 Disc florets all functionally staminate > 4
4 Cypselae arcuate to ± coiled, abaxially tuberculate, sometimes winged Calendula
4 Cypselae triquetrous-prismatic to clavate, ± tuberculate and/or winged Osteospermum
5 Margins of leaf blades usually 1–3-palmately or -pinnately lobed (ultimate lobes usually linear to filiform), sometimes dentate or entire; phyllaries in (2–)3–5+ series, unequal, and scarious or margins and/or apices notably scarious > 6
5 Margins of leaf blades entire, dentate, lobed, palmatifid, pinnatifid, or dissected (ultimate lobes sometimes linear to filiform); phyllaries in 1–2 series and ± equal to subequal, or in 3–8+ series and unequal, usually herbaceous to chartaceous, sometimes with margins and/or apices notably scarious > 19
6 Cypselae dimorphic: outer (ray) usually 3-angled and ± winged (except Mauranthemum); inner (disc) ± compressed-prismatic or ± flattened (angles winged), or ± quadrate (1 or 2 angles sometimes winged), or columnar (not winged) > 7
6 Cypselae ± monomorphic, outer and inner similar (none notably winged) > 11
7 Subshrubs or shrubs (plants often persisting after cultivation) Argyranthemum
7 Annuals > 8
8 Stems and leaves hirtellous to pilosulous (some hairs gland-tipped, plants sticky, viscid) Heteranthemis
8 Stems and leaves glabrous or hairy (hairs not gland-tipped, plants not viscid) > 9
9 Rays proximally white or red to purple, distally yellow or white; disc corollas proximally ochroleucous, distally red to purple (phyllaries ± carinate) Ismelia
9 Rays mostly white (usually yellowish at bases) or mostly yellow (sometimes paler distally); disc corollas ± yellow (phyllaries not carinate) > 10
10 Involucres 8–12(–15+) mm diam.; rays white (usually yellowish at bases, drying pinkish), laminae oblong to ovate (6–12+ mm); disc corolla lobes (2–)5 (without resin sacs) Mauranthemum
10 Involucres 15–25+ mm diam.; rays mostly yellow, sometimes paler distally, laminae linear, oblong, or ovate (8–25 mm); disc corolla lobes 5 (each with a resin sac) Glebionis
11 Annuals > 12
11 Biennials or perennials > 14
12 Leaves usually irregularly 1-pinnately lobed or toothed; involucres ± hemispheric, 8–12(–15+) mm diam.; disc florets 60–100+; cypsela ribs 7–10. Mauranthemum
12 Leaves (1–)2–3-pinnately lobed; involucres 4–14 mm diam.; disc florets 120–750+; cypsela ribs 3–5 > 13
13 Cypselae obconic, slightly compressed (usually asymmetric, apices oblique), ribs 5, faces smooth between ribs (pericarps without resin sacs, or resin sacs within lateral ribs) Matricaria
13 Cypselae trigonous, ± compressed, ribs 3–5 (0–2 abaxial, 2 lateral, 1 adaxial, usually whitish, relatively thick, smooth), faces smooth or rugose to tuberculate between ribs (pericarps usually with 2–3, sometimes 1–5 mostly abaxial-apical, resin sacs) Tripleurospermum
14 Heads usually in lax to dense, corymbiform arrays, rarely borne singly; pappi usually coroniform, rarely 0 Tanacetum
14 Heads usually borne singly or in 2s or 3s, sometimes in corymbiform arrays; pappi usually 0, sometimes crowns of 6–12 irregular teeth > 15
15 Ray florets styliferous and sterile Leucanthemella
15 Ray florets pistillate and fertile > 16
16 Cypselae trigonous, ± compressed, ribs 3–5 (0–2 abaxial, 2 lateral, 1 adaxial, usually whitish, relatively thick, smooth), faces smooth or rugose to tuberculate between ribs (pericarps usually with 2–3, sometimes 1–5 mostly abaxial-apical, resin sacs) Tripleurospermum
16 Cypselae ± columnar, cylindro-obconic, or obovoid, ribs 5–10 (pericarps without apical resin sacs) > 17
17 Plants (10–)50–130(–200+) cm; disc corolla tubes ± cylindric (proximally swollen, becoming spongy in fruit); cypselae ± columnar to obovoid, ribs ± 10 (pericarps with myxogenic cells) Leucanthemum
17 Plants mostly (2.5–)5–40 cm; disc corolla tubes ± cylindric (not swollen, not becoming spongy in fruit); cypselae cylindro-obconic, ribs 5–8(–10) (pericarps without myxogenic cells) > 18
18 Leaf margins entire; involucres 4–6.5 mm diam.; phyllaries 20–26(+) in 2(–3+) series (receptacles ± villous). Hulteniella
18 Leaf margins usually pinnati-palmately lobed (lobes 3–7), ultimate margins coarsely crenate, dentate, or entire; involucres 13–29 mm diam.; phyllaries 22–44 in 3(–4) series (receptacles glabrous) Arctanthemum
19 Leaves alternate; phyllaries in 1–2 series and equal to subequal (sometimes coherent, often subtended by calyculi); style-branch appendages usually penicillate or essentially none; cypselae usually ± columnar to prismatic, seldom compressed, obcompressed, or flattened > 20
19 Leaves whorled, opposite, or alternate; phyllaries in 1–2 series and subequal, or in 3–6+ series and unequal; style-branch appendages usually deltate to lanceolate, seldom penicillate or none; cypselae sometimes compressed, obcompressed, or flattened > 23
20 Perennials > 21
20 Annuals > 22
21 Rays usually whitish or bluish, pinkish, purplish, or reddish (often proximally pale and distally darker); disc floret style-branches: stigmatic areas in 2 lines. Pericallis
21 Rays yellow; disc floret style-branches: stigmatic areas continuous Doronicum
22 Disc florets functionally staminate (not producing cypselae, styles not divided); leaf blades linear or pinnately lobed, ultimate margins entire, faces glabrous or sparsely floccose-tomentose Blennosperma
22 Disc florets bisexual (fertile, styles 2-branched); leaf blades spatulate or oblanceolate to lanceolate or linear, margins toothed or entire, faces glabrous or glabrate Crocidium
23 Leaves opposite (at least proximally) > 24
23 Leaves alternate or mostly alternate (sometimes proximal opposite) > 32
24 Leaves and/or phyllaries dotted or streaked with pellucid (schizogenous) glands containing strong-scented (lemon or spicy) oils; ray florets borne on bases of subtending phyllaries Pectis
24 Leaves and/or phyllaries rarely dotted or streaked (never with pellucid, schizogenous glands containing strong-scented oils, plants sometimes with sessile or stipitate, surface glands and may be otherwise strong-scented); ray florets borne on receptacles > 25
25 Leaves (often ± succulent) sessile or nearly so, blades usually oblong to linear or filiform (not lobed); cypselae clavate to cylindric and 8–15-ribbed > 26
25 Leaves (seldom succulent) petiolate or sessile, blades often lobed; cypselae usually obpyramidal to obconic, sometimes columnar or flattened, seldom clavate or cylindric, often 4–5-angled (not both clavate to cylindric and 8–15-ribbed; sometimes cylindric and 5–10-nerved) > 27
26 Heads in tight, corymbiform aggregations or arrays; phyllaries 2–6(–9) in ± 1 series, subequal; rays 1(–2) Flaveria
26 Heads borne singly; phyllaries 12–15 in 3+ series, unequal; rays 3–10 Jaumea
27 Phyllaries often ± conduplicate and navicular; disc corollas 4-lobed; cypselae strongly flattened to subcylindric, ± callous-margined, often ciliate Perityle
27 Phyllaries usually flat to weakly navicular; disc corollas (4–)5-lobed; cypselae narrowly clavate or columnar to obconic or obpyramidal (not strongly compressed or flattened, callous-margined, and ciliate) > 28
28 Leaves usually sessile, sometimes obscurely petiolate, blades (or lobes) linear, margins entire or 1–2-pinnately lobed Lasthenia
28 Leaves usually petiolate, sometimes sessile, blades rounded-deltate or cordate to ovate, narrowly trullate, lanceolate, linear, obovate, oblanceolate, or cuneate to spatulate, margins entire, toothed, or distally 3-lobed (not 1–2-pinnately lobed) > 29
29 Phyllaries 20–40+ in 3–4+ series; rays 12–34, yellow Venegasia
29 Phyllaries 5–18 in 1–3 series; rays 5–12, yellow, or white or pinkish with reddish veins > 30
30 Leaf blades either linear and margins entire, or narrowly cuneate to spatulate and margins usually distally 3-lobed; phyllaries 5–8 in 1 series; rays either yellow, or white or pinkish with reddish veins Syntrichopappus
30 Blades lanceolate, narrowly trullate, oblanceolate, obovate, margins entire or denticulate; phyllaries 5–18 in 1–3 series; rays yellow > 31
31 Phyllaries 5–12 in 1 series Arnica
31 Phyllaries 14–18 in ± 3 series Jamesianthus
32 Rays white, pink, purple, or blue > 33
32 Rays usually yellow to orange, sometimes red > 41
33 Receptacles conic > 34
33 Receptacles flat to convex > 37
34 Leaves usually pinnatifid to dentate, sometimes entire; rays without midstripe abaxially; cypselae not or slightly compressed > 35
34 Leaves usually entire, sometimes ± toothed; rays usually with pink or purplish midstripe abaxially; cypselae strongly compressed or flattened > 36
35 Plants gland-dotted; cypselae oblong to narrowly obovoid, slightly compressed, 2-nerved, sometimes gland-dotted Egletes
35 Plants eglandular; cypselae columnar to prismatic, usually 4-angled, 4–12-ribbed (ribs relatively thick), eglandular Aphanostephus
36 Perennials 5–20 cm (short-rhizomatous); leaves mostly basal, margins entire or crenate-serrate; rays 35–90 in 3–4 series (closing at night); cypselae obconic, glabrous to short-strigose or ciliate-margined Bellis
36 Annuals, biennials, or perennials, 5–50 cm (tap- or fibrous-rooted); leaves basal and cauline, margins usually entire, sometimes toothed; rays 10–65(–85) in 1 series; cypselae obovoid to oblanceoloid- obovoid, glabrous or glochidiate-hairy Astranthium
37 Leaves mostly basal or basal and cauline, margins 1–2-pinnately lobed (lobes usually filiform); rays 8, white; cypselae obpyramidal (4- or 5-angled, faces 1–4-ribbed) Hymenopappus
37 Leaves basal (usually withering by flowering) or mostly cauline, margins entire or toothed, sometimes 1-pinnately lobed (lobes not usually filiform); rays (1–)3–70, white or pink to blue or purple; cypselae linear, fusiform, clavate, oblanceoloid, obovoid, or obconic, ± flattened or ± compressed to ± cylindric, sometimes 2–18-nerved > 38
38 Phyllaries 5–8 in 1 series, subequal; rays white or pinkish with reddish veins Syntrichopappus
38 Phyllaries 5–50 in 2–6 series, equal to unequal; rays white or blue to purple (not with reddish veins) > 39
39 Disc corolla lobes 4 Perityle
39 Disc corolla lobes 5 > 40
40 Heads borne singly (terminal); phyllaries in 2–3 series, equal to subequal, faces eglandular Chaetopappa
40 Heads in loose, corymbiform arrays; phyllaries in 2–6 series, unequal, (herbaceous) faces stipitate-glandular Psilactis
41 Disc corollas usually 4-lobed; cypselae usually callous-margined and ciliate Perityle
41 Disc corollas 5-lobed; cypselae not callous-margined or notably ciliate > 42
42 Subshrubs or shrubs > 43
42 Annuals, biennials, or perennials > 46
43 Heads (± sessile) in compact glomerules (glomerules densely clustered in terminal, corymbiform arrays); involucres 1.5–2 mm diam.; rays 4–6; disc florets 4– 6 Gymnosperma
43 Heads (± pedunculate) borne singly or in corymbiform to paniculiform arrays (not in glomerules); involucres 5–25 mm diam.; rays 5–60+; disc florets 20–300 > 44
44 Phyllaries in 5–8+ series, apices (terete to filiform or subulate) recurved or straight, or looped to hooked or patent Grindelia
44 Phyllaries in 1–4 series, apices usually straight, not recurved, looped, hooked, or patent > 45
45 Leaf blades usually 1–2(–3)-pinnately lobed, ultimate margins entire or toothed, faces ± woolly; involucres campanulate to hemispheric, 3–12+ mm diam.; phyllaries in 1+ series (sometimes ± connate) Eriophyllum
45 Leaf blades rounded-deltate or cordate to ovate, entire or toothed, abaxial faces puberulent or gland-dotted; involucres hemispheric to globose, 12–25+ mm diam.; phyllaries in 3–4 series (outer rotund to oblong, herbaceous-foliaceous) Venegasia
46 Ray florets usually neuter, rarely pistillate and fertile or styliferous and sterile (disc corolla lobes often shaggily hairy, hairs ± moniliform) Gaillardia
46 Ray florets pistillate, fertile > 47
47 Ray florets in 2 series (staminodes often present), adaxial faces of inner laminae marked basally with purple-brown fans 1/4–1/8 their lengths Arctotis
47 Ray florets in 1 series (without staminodes), adaxial faces of laminae not marked basally with purple-brown > 48
48 Phyllaries 25–100+ in (3–)4–9+ series, apices (terete to filiform or subulate) recurved or straight, or looped to hooked or patent Grindelia
48 Phyllaries 5–40 in 1–4 series, apices usually straight, not recurved, looped, hooked, or patent > 49
49 Leaf blades simple, margins entire, spinulose-toothed, or sinuate-dentate (not lobed) > 50
49 Leaf blades 1–2(–3)-pinnately or -ternately lobed, pinnatifid, or distally 3-lobed > 53
50 Phyllaries 30–40 in 2–4 series (annuals; leaf blades oblanceolate, margins entire or spinulose-toothed, faces glabrous, gland-dotted; rays 14– 63) Xanthocephalum
50 Phyllaries 2–34 in 1–2(–3) series > 51
51 Leaf blades linear to lanceolate, margins entire; disc florets 10–21, functionally staminate Amphiachyris
51 Leaf blades narrowly oblong, oblanceolate, or lance-linear, margins sinuate-dentate or entire; disc florets 10–100+, bisexual, fertile > 52
52 Leaf blades narrowly oblong, oblanceolate, or lance-linear, margins sinuate-dentate or entire; heads usually borne singly (sometimes in corymbiform arrays); phyllaries in 1 series, distinct; cypselae obcompressed or ± prismatic, 2–4-angled. Monolopia
52 Leaf blades lance-linear to broadly ovate, margins entire; heads borne singly or in cymiform arrays; phyllaries in 2 series, distinct or connate; cypselae narrowly obpyramidal, weakly ribbed or striate Baileya
53 Phyllaries in 1 series > 54
53 Phyllaries in 2–3+ series > 56
54 Leaf blades distally 3-lobed Syntrichopappus
54 Leaf blades usually 1–2(–3)-pinnately lobed > 55
55 Ray cypselae obcompressed (disc corollas with rings of hairs at bases of limbs) Pseudobahia
55 Ray cypselae usually prismatic, 4–5-angled (disc corollas with- out rings of hairs) Eriophyllum
56 Cypselae obpyramidal (lengths usually 3+ times diams.) Amauriopsis
56 Cypselae stoutly obconic to obpyramidal (lengths usually 1–2, rarely to 3.5 times diams.) > 57
57 Phyllary margins usually notably membranous to scarious; disc corollas usually whitish, sometimes purplish or yellowish; cypselae usually 4-angled and 12–16-ribbed Hymenopappus
57 Phyllary margins seldom scarious; disc corollas yellow or partly yellow-brown proximally; cypselae sometimes weakly ribbed or striate (not both 4-angled and 12–16-ribbed) > 58
58 Receptacles usually hemispheric, globoid, ovoid, conic (seldom flat); ray florets 3–16 (corollas withering, falling early or tardily) Hymenoxys
58 Receptacles flat to convex; ray florets usually 5–7 or 20– 55 (corollas usually marcescent) Baileya

Key to Genera of Group 9 Heads radiate; receptacles epaleate; ray corollas white, pink, or purple (with little, if any, yellow); pappi wholly of bristles (without awns or scales)

1 Cauline leaves opposite (at least proximal) > 2
1 Cauline leaves all alternate > 3
2 Leaves sessile; leaves and phyllaries dotted with pellucid (schizogenous) glands contain- ing strong-scented oils Pectis
2 Leaves petiolate or sessile; leaves and phyllaries sparsely tomentose to woolly or glabrescent (without schizogenous glands) Syntrichopappus
3 Phyllaries in 1–2 series, equal > 4
3 Phyllaries in 2–7+ series, unequal to subequal (pappi persistent, bristles usually barbellate, sometimes barbellulate) > 8
4 Pappi persistent, either 1 apically plumose bristle (plus short-toothed cups) or 1–12 bristles (often alternating with easily overlooked, laciniate scales) Monoptilon
4 Pappi falling or persistent (fragile), usually 20–100+ barbellulate or smooth (barbellate in Pericallis) bristles > 5
5 Disc florets (all or mostly) functionally staminate (not producing cypselae) Petasites
5 Disc florets (all or mostly) bisexual, fertile > 6
6 Phyllary margins not interlocking; ray corollas usually whitish or bluish, pinkish, purplish, or reddish (often proximally pale and distally darker); pappi readily falling, usually of 20–40+ bristles (discs; rays sometimes of 2 subulate to setiform scales or 0) Pericallis
6 Phyllary margins interlocking; ray corollas usually white (with little, if any, yellow), rarely purplish to reddish; pappi persistent or readily falling, usually of 30–80+ bristles > 7
7 Calyculi of (0–)1–8+ bractlets; disc corolla tubes shorter than or equaling throats; style branches stigmatic in 2 lines (stamen filaments usually distally expanded into swollen collars); cypselae 5-ribbed or -angled Senecio
7 Calyculi none; disc corolla tubes equaling or longer than throats; style branches with continuous stigmatic areas (stamen filaments cylindric, not distally expanded); cypselae 10-ribbed or -nerved Tephroseris
8 Subshrubs or shrubs (clambering, sprawling, or vinelike) > 9
8 Annuals, biennials, or perennials > 17
9 Shrubs (clambering, sprawling, or vinelike); rays pale rose-purple to pale pink (Atlantic coastal plain) Ampelaster
9 Subshrubs or shrubs (not clambering, sprawling, or vinelike); rays white, pink, red-purple, purple, or violet > 10
10 Plants often thorny (thorns green); rays white; disc corolla veins orange, resinous Chloracantha
10 Plants not thorny; rays white, pink, red-purple, purple, or violet; disc corolla veins not orange-resinous > 11
11 Stems, leaves, and phyllaries resinous; leaf margins entire; phyllaries 18–24, midnerves expanded, faces glabrous Neonesomia
11 Stems and phyllaries not resinous (leaves sometimes resinous in Hazardia); leaf margins entire or toothed or serrate (spinulose or bristly); phyllaries (15–)20–90+, midnerves not expanded, faces glabrous or hairy, sometimes stipitate-glandular > 12
12 Ray florets neuter; cypselae cuneiform to linear, not compressed Corethrogyne
12 Ray florets bisexual, fertile; cypselae obscurely cordate, deltoid, ovoid, ellipsoid, oblong, obovoid, cylindro-obconic, fusiform, or linear, usually ± compressed > 13
13 Cypselae dimorphic (ray 3-sided, disc compressed), obscurely cordate, ellipsoid, oblong, or obovoid Xanthisma
13 Cypselae monomorphic (usually ± compressed), deltoid, ovoid, obovoid, cylindro-obconic, fusiform, or linear > 14
14 Cypselae 7–10-nerved Herrickia
14 Cypselae 2–5-ribbed or -nerved > 15
15 Phyllaries in 5–9 series, not keeled; pappi reddish brown Hazardia
15 Phyllaries in 2–6 series, keeled; pappi stramineous to tawny > 16
16 Cypselae flattened, 2–3(–4)-nerved; pappi of outer, shorter bristles or scales plus inner, longer bristles. Ionactis
16 Cypselae compressed, 4–5-ribbed; pappi of ± unequal bristles Xylorhiza
17 Annuals or biennials > 18
17 Perennials > 29
18 Disc corolla veins orange-resinous > 19
18 Disc corolla veins not orange-resinous > 22
19 Heads borne singly Chaetopappa
19 Heads usually in corymbiform or paniculiform arrays, sometimes borne singly > 20
20 Disc corolla throats slightly indurate and inflated Erigeron
20 Disc corolla throats narrowly funnelform (not indurate and inflated) > 21
21 Leaf faces often stipitate-glandular or gland-dotted; phyllaries lacking orange to brown midnerves; cypselae densely sericeous, ± strigillose, or glabrous, often stipitate-glandular and/or gland-dotted Laënnecia
21 Leaf faces eglandular; phyllaries with orange to brownish midnerves; cypselae glabrous or strigillose, eglandular Conyza
22 Pappus bristles usually 5 Pentachaeta
22 Pappus bristles usually 20–80+ (ray sometimes 0) > 23
23 Stems glabrous (or distally hairy in lines only), eglandular; ray florets 90– 110 in 4–5 series (laminae filiform) Symphyotrichum
23 Stems glabrous or hairy, often stipitate-glandular as well; ray florets (4–)7–80 in 1 series (laminae usually strap-shaped) > 24
24 Heads in corymbiform arrays; phyllaries in 2–3 series; ray pappi none Psilactis
24 Heads usually borne singly (at ends of branches, leafy stems, or scapi-form peduncles), sometimes in cymiform or corymbiform arrays; phyllaries in 3–12+ series; ray pappi usually present (usually none in Arida) > 25
25 Cypselae 2(–3)-nerved Townsendia
25 Cypselae smooth (at most obscurely nerved) or 4–13-ribbed or -nerved per face > 26
26 Leaves deeply 1–-2-pinnatifid (some or all lobes or teeth acute and bristle-tipped) Machaeranthera
26 Leaves usually entire, toothed, or lobed (if 1–2-pinnatifid, teeth or lobes often rounded, sometimes apiculate, mostly not bristle-tipped) > 27
27 Cypselae ± obconic, not compressed, smooth (at most obscurely nerved); pappus bristles distinct or basally connate, tan to reddish Lessingia
27 Cypselae linear to narrowly obovoid or narrowly oblong, 4–13-ribbed or -nerved; pappus bristles distinct, white to tawny > 28
28 Plants hairy, sometimes stipitate-glandular; leaves entire or toothed; ray pappi of 40–50 bristles. Dieteria
28 Plants glabrous and leaves entire or toothed (ciliate or teeth bristle-tipped or apiculate), or plants hairy, sometimes stipitate-glandular, and leaves 1–2-pinnatifid; ray pappi usually 0 (if 20–30 bristles, leaves 1–2-pinnatifid) Arida
29 Plants colonial; stems branched, lateral branches strongly ascending, commonly modified to green thorns; leaves early withering; phyllaries (1–)3(–5)-nerved (usually wet sites in arid, sw United States) Chloracantha
29 Plants sometimes colonial; stems single or clustered, simple or branched (not becoming thorny); at least distal leaves persistent through flowering; phyllaries usually 1-nerved, seldom 3-nerved > 30
30 Cypselae usually obconic or obovoid, sometimes lanceoloid, flattened or compressed, margins ribbed (sometimes also 1–2 nerves on faces) > 31
30 Cypseale ± narrowly obconic, obovoid, oblanceoloid, ellipsoid, lanceoloid, or fusiform, to cylindric or linear, ± compressed or terete, usually 3–12+-nerved or -ribbed on faces (margins not ribbed) > 35
31 Leaves cauline; phyllaries keeled > 32
31 Leaves basal and/or cauline; phyllaries not keeled > 33
32 Plants 10–160 cm, minutely stipitate-glandular distally; proximal leaves withering by flowering, proximalmost scalelike, cauline distally increasing in size to mid stems, mid and distal blades lanceolate or lance-ovate to elliptic; heads in racemiform or corymbiform arrays (pappi of outer, shorter and inner, longer bristles in 3 series) Eucephalus
32 Plants 4–30(–70) cm, sometimes stipitate-glandular; leaves persistent to flowering, mostly equal in size and shape, blades spatulate (proximal), linear, narrowly oblong, or elliptic-lanceolate; heads borne singly or in 2s or 3s, or in corymbiform arrays Ionactis
33 Leaf faces eglandular; corolla lobes lanceolate Aster
33 Leaf faces often gland-dotted; corolla lobes deltate or lance-deltate > 34
34 Plants taprooted or with branched caudices; heads borne singly; leaves usually entire, rarely toothed or lobed; phyllaries unequal, 1-nerved (nerves not golden-resinous); disc corolla throats funnelform; cypselae glabrous or hairy (hairs glochidiform) Townsendia
34 Plants rhizomatous, sometimes taprooted; heads borne singly or in corymbiform arrays; leaves entire, ± dentate, or pinnatifid; phyllaries equal or unequal, 1–3-nerved (nerves golden-resinous); disc corolla throats usually tubular, sometimes strongly inflated-indurate; cypselae glabrous, strigose, or sericeous Erigeron
35 Cypselae ± dimorphic (ray 3-sided and rounded abaxially, disc ± compressed); pappi of relatively coarse (± flattened) bristles > 36
35 Cypselae monomorphic; pappi of relatively fine bristles > 37
36 Stems simple; leaves mostly basal, margins serrate or serrulate; involucres depressed-hemispheric; cypselae 3–9-ribbed per face; pappus bristles coarsely barbellate Xanthisma
36 Stems usually branched; leaves basal (persistent or withering by flowering) and cauline (distally ± reduced) or mostly cauline, margins pinnately lobed or pinnatifid, toothed, or entire; involucres turbinate, campanulate, or hemispheric; cypselae 8–13-nerved per face; pappus bristles barbellulate Arida
37 Anther bases tailed Sachsia
37 Anther bases rounded, obtuse, or acute (not tailed) > 38
38 Plants rhizomatous, sometimes with caudices; heads usually in paniculiform or racemiform arrays, rarely borne singly > 39
38 Plants taprooted, with caudices, or rhizomatous; heads usually in corymbiform (or flat-topped, racemiform) arrays or borne singly, sometimes grouped in loose, corymbiform arrays > 42
39 Stems spreading-hirsute, eglandular; heads in narrow wand-shaped, paniculiform arrays; phyllary midribs translucent and swollen; rays 7–9 (corollas white to pale cream) Solidago
39 Stems usually glabrous, often distally hairy in lines, sometimes ± densely hairy, sometimes distally stipitate-glandular; heads in ± open or dense (not wand-shaped), paniculiform arrays; phyllary midnerves not translucent and swollen; rays 8–75 (corollas white, pink, blue, or purple) > 40
40 Phyllaries usually unequal, sometimes subequal, proximally indurate, distally with defined green zones, sometimes distally herbaceous or outer wholly foliaceous, sometimes stipitate-glandular Symphyotrichum
40 Phyllaries subequal, herbaceous (without definite distal green zones, not foliaceous), stipitate-glandular > 41
41 Stems ± densely villous; leaves cauline, blades 1-nerved (venation reticulate), lanceolate to elliptic, abaxial faces glabrate to ± strigose, adaxial sparsely villous (distal stipitate-glandular); phyllaries often purplish, apices of outer acuminate; cold, wet soils, montane and boreal North America Canadanthus
41 Stems glabrous; leaves basal and cauline, blades 3-nerved, linear, faces glabrous (distal stipitate-glandular); phyllaries green, apices of outer acute; damp, alkaline areas, deserts and dry prairies, w North America Almutaster
42 Plants usually tapooted, sometimes with caudices (plus also rhizomatous from fibrous roots in Chaetopappa); stems usually 1 (sometimes 2–5+ in clumps), branched or simple; heads borne singly or in loose, corymbiform arrays > 43
42 Plants rhizomatous or with caudices; stems 1–5+, usually simple; heads usually in corymbiform arrays, sometimes borne singly (then plants long-rhizomatous, rays pink) > 48
43 Stems and leaves usually densely white-tomentose, sometimes glabrate; ray florets neuter; cypselae cuneiform or linear; pappi reddish to brownish (bristles relatively coarse, California) Corethrogyne
43 Stems and leaves glabrous, glabrate, canescent, villous, or tomentose; ray florets pistillate, fertile; cypselae fusiform, cylindric, obovoid, or linear; pappi hyaline or white to tawny > 44
44 Stems simple; leaf margins entire; phyllaries mostly foliaceous (margins sometimes proximally indurate); rays white (maturing or drying bluish or purplish) > 45
44 Stems branched or simple; leaf margins entire or toothed (teeth spine-tipped); phyllaries proximally white-indurate, distally green or herbaceous (usually not foliaceous); rays white, blue, violet, or purple > 46
45 Leaves basal and cauline (crowded), blades 1-nerved, linear-oblanceolate to lanceolate; phyllaries not keeled; cypselae 5-nerved Chaetopappa
45 Leaves mostly basal (rosettes), blades 3-nerved, linear to oblanceolate; phyllaries often ± keeled; cypselae 5–10-nerved (nerves raised) Oreostemma
46 Stems mostly simple (scapiform); leaves mostly basal (rosettes, often marcescent), margins entire or irregularly serrate (teeth apiculate or ± spinulose); phyllaries squarrose; cypselae 8–10-ribbed (canyons, rock faces, Utah) Herrickia
46 Stems mostly branched; leaves basal and cauline, margins entire or toothed (teeth spinose-tipped); phyllaries appressed, spreading, or reflexed; cypselae 4-nerved, 4–6-ribbed, or smooth > 47
47 Stems mostly single; cauline leaf blades lanceolate to oblan- ceolate; phyllaries not keeled Dieteria
47 Stems clustered; cauline leaf blades usually spatulate to obovate or oblong, rarely elliptic; phyllaries keeled Xylorhiza
48 Phyllaries flat, not keeled, midveins orange-resinous or swollen and translucent > 49
48 Phyllaries ± rounded, sometimes ± keeled, midveins not swollen > 50
49 Plants 40–200 cm; leaves basal (withering, reduced) and cauline, blades 1-nerved, lanceolate to elliptic; phyllary midveins orange-resinous; rays 2–10(–16) Doellingeria
49 Plants 10–40 cm; leaves basal (persistent, well developed) and cauline (reduced), blades usually 1-nerved, sometimes ± 3-nerved, linear to linear-lanceolate, phyllary midveins swollen, translucent; ray florets 10–20 Solidago
50 Rhizomes with swollen apical buds; heads in ± loose, corymbiform arrays or borne singly (nodding in bud); phyllaries lance-ovate to linear (membranous, proximally not indurate, green along midnerves); cypselae 5–8-nerved (lateral 2 thicker), ± densely gland-dotted (e North America) Oclemena
50 Rhizomes none or not apically swollen; heads in corymbiform arrays (erect in bud); phyllaries ovate, oblong, lanceolate, or linear-lanceolate (proximally indurate, distally with sharply delimited green apical zones); cypselae 7–12(–18)-nerved, eglandular > 51
51 Involucres cylindric; rays 1–6, white; disc corollas white or cream; cypselae ± densely strigose Sericocarpus
51 Involucres cylindro-campanulate or campanulate; rays 5–60, white to purple; disc corollas yellow; cypselae glabrous or ± densely strigillose > 52
52 Stems and leaves usually stipitate-glandular, sometimes eglandular and glaucous; leaves mostly cauline, entire or spinulose-serrate, glabrous or scabrellous; phyllaries usually keeled, sometimes rounded, apices acute to long-acuminate; rays 8–27; disc corolla tubes shorter than throats (w Cordilleras) Herrickia
52 Stems and leaves usually eglandular, sometimes stipitate-glandular (e North America only), not glaucous; leaves basal and/or cauline, serrate (teeth sometimes spinose, then blades linear, grasslike, se North America) or entire, hairy or glabrous; phyllaries usually rounded, sometimes keeled, apices obtuse to acute; rays 5–60; disc corolla tubes shorter or longer than throats. Eurybia

Key to Genera of Group 10. Heads radiate; receptacles epaleate; ray corollas yellow, orange, red, or brown; pappi wholly of bristles

1 Leaves opposite (at least proximally, or if mostly basal and subopposite or alternate, cypselae obcompressed, each shed with a subtending, linear, membranous scale) > 2
1 Leaves all alternate > 8
2 Leaves and/or phyllaries dotted or streaked with pellucid (schizogenous) glands containing strong-scented oils > 3
2 Leaves and/or phyllaries not dotted or streaked (never with pellucid, schizogenous glands containing strong-scented oils, plants sometimes with sessile or stipitate, surface glands and may be otherwise strong-scented) > 4
3 Annuals or perennials; ray florets borne on bases of subtending phyllaries; style branches of bisexual disc florets knob-like Pectis
3 Subshrubs or shrubs; ray florets borne on receptacles; style branches of bisexual disc florets linear Chrysactinia
4 Leaves (somewhat succulent) sessile or nearly so, filiform to linear, margins entire; phyllaries 2–5 in 1 series Haploësthes
4 Leaves (seldom succulent) usually petiolate, sometimes ± sessile, blades cordate, deltate, elliptic, lanceolate, narrowly trullate, linear, oblanceolate, oblong, obovate, ovate, cuneate, or spatulate, margins entire, toothed, or distally 3-lobed; phyllaries 5–23 in 1–3 series > 5
5 Leaves all or nearly all opposite (distalmost cauline sometimes alternate and usually smaller) > 6
5 Leaves alternate and either proximal opposite or leaves mostly basal (sometimes subopposite) > 7
6 Phyllaries 8–23 in (1–)2 series (subequal); pappi persistent, of 10–50 bristles Arnica
6 Phyllaries 14–18+ in ± 3 series (unequal); pappi fragile, of 6–8+ bristles Jamesianthus
7 Phyllaries 8–22 in 2–3 series; cypselae obcompressed (each shed together with a subtending, linear, membranous scale, margins ciliate); pappi of distinct bristles Bartlettia
7 Phyllaries 5–8 in 1 series; cypselae narrowly obconic, clavate, or fusiform (margins not ciliate); pappi of basally connate or coherent bristles. Syntrichopappus
8 Style-branch appendages usually penicillate or essentially 0 > 9
8 Style-branch appendages usually deltate to lanceolate, seldom penicillate > 25
9 Phyllaries in (2–)3–7+ series, unequal to subequal (distinct, calyculi 0); pappi of (± coarse) barbellate bristles > 10
9 Phyllaries in 1–2 series, equal to subequal (sometimes coherent, often subtended by calyculi); pappi of (fine) smooth or barbellulate bristles > 11
10 Annuals (pilosulous to hispid and stipitate-glandular, viscid); involucres 3–8 mm diam.; ray laminae 2–5(–7) mm Dittrichia
10 Perennials; involucres 10–40 mm diam.; ray laminae 10–30+ mm Inula
11 Shrubs or vines > 12
11 Annuals, biennials, perennials, or subshrubs > 14
12 Vines (usually ± twining and climbing; corollas orange to ± brick-red; Florida) Pseudogynoxys
12 Shrubs > 13
13 Leaves (or lobes) linear (± evenly distributed) Senecio
13 Leaves lance-elliptic or lanceolate to lance-linear (clustered distally on branches; Arizona and New Mexico) Barkleyanthus
14 Annuals > 15
14 Biennials, perennials, or subshrubs > 18
15 Receptacles dome-shaped to conic (heights equaling or greater than diameters) Crocidium
15 Receptacles flat to convex (sometimes ± dome-shaped in Tephroseris) > 16
16 Style branches: stigmatic areas continuous (stamen filaments cylindric, not distally expanded) Tephroseris
16 Style branches: stigmatic in 2 lines (stamen filaments distally expanded into swollen collars) > 17
17 Leaves basal and/or cauline (roots often fleshy and seldom branched and/or leaf margins with many callous denticles). Senecio
17 Leaves basal and cauline (roots seldom fleshy, often branched; leaf margins with few or no callous denticles) Packera
18 Disc florets (all or mostly) functionally staminate (not producing cypselae) Tussilago
18 Disc florets (all or mostly) bisexual, fertile > 19
19 Style branches: stigmatic in 2 lines (stamen filaments usually distally expanded into swollen collars) > 20
19 Style branches: stigmatic areas continuous (stamen filaments cylindric, not distally expanded) > 21
20 Leaves basal and/or cauline (roots often fleshy and seldom branched and/or leaf margins with relatively many callous denticles) Senecio
20 Leaves basal and cauline (roots seldom fleshy, often branched; leaf margins with relatively few or no callous denticles) Packera
21 Petiole bases usually dilated (sheathing stems); laminae of ray corollas orange to orange-yellow or brick-red (20–50 mm); pappi reddish (Maryland) Ligularia
21 Petiole bases rarely dilated (except Doronicum and Sinosenecio); laminae of ray corollas usually yellow, sometimes yellow-orange or orange; pappi white or stramineous to brownish > 22
22 Phyllaries in 2–3+ series, margins seldom scarious (often ciliate); rays 21–40+ (ray cypselae often epappose) Doronicum
22 Phyllaries in (1–)2 series, margins ± scarious (seldom ciliate); rays mostly 5, 8, 13, or 21 > 23
23 Leaf blades (at least proximal) suborbiculate (lengths mostly 1–1.5 times widths and plants 60–300 cm); corolla tubes usually glandular-puberulent (s Arizona) Roldana
23 Leaf blades seldom suborbiculate (lengths mostly 3–10+ times widths; if suborbiculate, plants 3–60+ cm); corolla tubes seldom, if ever, glandular-puberulent > 24
24 Leaf blades pinnately nerved, lanceolate, linear-oblanceolate, oblanceolate, ovate, or subrhombic. Tephroseris
24 Leaf blades palmately or subpalmately nerved, ovate to subreniform (British Columbia) Sinosenecio
25 Subshrubs or shrubs > 26
25 Annuals, biennials, or perennials > 37
26 Phyllaries unequal and all disposed in vertical ranks > 27
26 Phyllaries equal or unequal and usually disposed in spirals > 29
27 Leaves basal and cauline, blades 3–5-nerved (veins raised, parallel) Petradoria
27 Leaves cauline, blades 1-nerved (sometimes with 1–2 fainter lateral pairs, not raised and parallel) > 28
28 Involucres cylindric, 5–6 mm; phyllaries 8–12, stramineous, flat, midnerves orange-resinous; rays 1–3; disc florets 2–5; cypselae densely strigoso- sericeous Chrysoma
28 Involucres cylindric, obconic, or hemispheric, 4–15 mm; phyllaries 13–30, green to tan, flat to keeled, midnerves sometimes evident, sometimes enlarged subapically and glandular (not orange-resinous); rays (1–)6–8; disc florets 4–15; cypselae glabrous or densely hairy Lorandersonia
29 Plants spinescent (at least with age) Amphipappus
29 Plants not spinescent > 30
30 Basal leaves pinnatifid (lobes bristle-tipped); pappus bristles basally flattened Xanthisma
30 Basal leaves not pinnatifid; pappus bristles not basally flattened > 31
31 Leaves entire or toothed (bases clasping or subclasping); heads usually in spiciform, racemiform, paniculiform, subumbelliform, or corymbiform arrays, rarely borne singly > 32
31 Leaves entire (bases not clasping); heads borne singly or in cymiform, spiciform, corymbiform, or racemiform (sometimes paniculiform or thyrsiform) arrays > 33
32 Leaves (teeth sometimes bristly) glabrous or densely tomentose (hairs not flagelliform); heads in spiciform, racemiform, narrowly paniculiform, or corymbiform arrays; phyllaries in 5–9 series; pappi of 20–30 reddish brown bristles in 1–2 series Hazardia
32 Leaves (teeth not bristly) densely short-woolly (hairs flagelliform); heads in subumbelliform to paniculiform arrays; phyllaries in 3–5 series; pappi of outer, triangular scales plus 20–40 inner bristles in (2–)3 series; e North America Chrysopsis
33 Shrubs > 34
33 Subshrubs > 35
34 Involucres hemispheric, obconic, or cylindric; disc corolla lobes equal; cypselae prismatic Ericameria
34 Involucres turbinate; disc corolla lobes unequal; cypselae ± turbinate Neonesomia
35 Stems prostrate to erect, mat-forming, branched; leaves cauline (crowded); heads borne singly Nestotus
35 Stems erect, not mat-forming, branched or simple; leaves basal and cauline or mostly cauline (then not crowded); heads in spiciform, racemiform, or corymbiform arrays, or glomerate and/or pedunculate-solitary in flat-topped or multi-storied, corymbiform arrays > 36
36 Plants rhizomatous; leaves 1–3(–5)-nerved, linear to lanceolate, gland-dotted; heads usually glomerate, sometimes pedunculate-solitary, in flat-topped or multi-storied, corymbiform arrays Euthamia
36 Plants stoutly taprooted; leaves 1-nerved, oblanceolate, eglandular or obscurely gland-dotted; heads (not glomerate) in racemiform or loose, spiciform or corymbiform arrays Columbiadoria
37 Pappi of easily overlooked setae or scales plus inner, longer bristles in 2+ series > 38
37 Pappi of bristles in 1–4 series (seldom with notably shorter bristles, scales, or setae) > 42
38 Plants taprooted or with simple caudices (and fibrous-rooted); heads borne singly or in 2s or 3s; phyllaries in 2–3 series, equal or subequal, flat, usually 1–3-nerved (nerves golden-resinous); cypselae 2-nerved, not resinous Erigeron
38 Plants taprooted, rhizomatous, or with branched caudices; heads usually in corymbiform, ± paniculiform, or subumbelliform arrays, sometimes borne singly; phyllaries in 3–5 series, unequal, usually thickened or keeled (not in Bradburia), 1-nerved (nerves not golden-resinous); cypselae smooth or 1–14-nerved or -ribbed, nerves or ribs sometimes resinous > 39
39 Stems and leaves silky-sericeous, rarely glabrate; leaves sessile, blades 3–11-parallel-nerved (nerves sunken), linear to lanceolate or ovate (often grasslike), margins entire; involucres turbinate Pityopsis
39 Stems and leaves whitish-strigose, pilose, or hispid, or arachnose to woolly (hairs flagelliform, soft), or glabrous; leaves sessile or basal petiolate, blades usually 1-nerved (veins reticulate, raised abaxially), spatulate, ovate-oblanceolate, ovate, elliptic, elliptic-oblong, oblanceolate, linear-lanceolate, or (usually distal) linear, margins entire, serrate, or dentate (sometimes coarsely ciliate); involucres campanulate or turbinate > 40
40 Plants proximally woolly, distally arachnose or pilose (hairs flagelliform); basal leaves sessile Chrysopsis
40 Plants sparsely to ± densely hispid, strigose, or pilose (hairs not flagelliform); basal leaves petiolate > 41
41 Perennials (taproots relatively short and/or caudices woody); basal petioles ciliate; cauline leaves much reduced distally, not clasping; heads borne singly or in lax, paniculiform arrays; cypselae monomorphic, ray pappi of outer, shorter, setiform scales or bristles plus inner, longer bristles Bradburia
41 Perennials (caudices woody); basal petioles long-strigoso-ciliate; cauline leaves ± reduced distally, sometimes clasping or subclasping; heads borne singly or in corymbiform, sometimes paniculiform arrays; cypselae dimorphic or monomorphic, ray pappi 0, or of outer, linear-lanceolate scales plus inner, longer bristles Heterotheca
42 Cypselae dimorphic (rays often ± 3-angled, discs ± compressed) > 43
42 Cypselae monomorphic (all ± compressed or all ± 3-angled) > 44
43 Heads borne singly or in corymbiform arrays (peduncles not cobwebby); involucres 4–10 mm; disc corolla throats gradually ampliate, ± funnelform; style-branch appendages lanceolate Xanthisma
43 Heads borne singly or (2–3) in paniculiform or subcorymbiform-cymiform arrays (peduncles often cobwebby); involucres 7–16 mm; disc corolla throats abruptly ampliate, funnelform; style-branch appendages deltate Rayjacksonia
44 Leaves 3-nerved (nerves ± parallel), faces thin-arachnose (in minute, abaxial lacunae) Croptilon
44 Leaves usually 1-nerved (sometimes 1–5-nerved), faces glabrous or ± hairy (not thin-arachnose in abaxial lacunae) > 45
45 Cypselae compressed, each edge 1-nerved Laënnecia
45 Cypselae sometimes ± compressed, each edge not 1-nerved > 46
46 Annuals > 47
46 Perennials > 50
47 Heads borne singly (at tips of branches); involucres eglandular; cypselae oblanceoloid or fusiform and (3–)5-ribbed or -nerved > 48
47 Heads borne singly or in corymbiform arrays; involucres glandular; cypselae clavate and 3-nerved or obconic and obscurely nerved > 49
48 Involucres campanulate to turbinate; phyllaries equal or subequal; cypselae oblanceoloid, 3–5-nerved, not beaked; pappus bristles (3–)5–20 (usually in multiples of 5) in 1 series Pentachaeta
48 Involucres ± cylindric to turbinate or obconic; phyllaries unequal; cypselae ± fusiform, 5-nerved, beaked; pappus bristles (12–)30–40 in (1–)2 series (outer shorter) Tracyina
49 Disc florets functionally staminate Benitoa
49 Disc florets bisexual, fertile (corollas of peripheral florets some- times palmately expanded, resembling rays) Lessingia
50 Heads usually glomerate and/or sometimes pedunculate-solitary in flat-topped or multi- storied, corymbiform arrays Euthamia
50 Heads borne singly or in spiciform, racemiform, paniculiform, or corymbiform arrays (if glomerate, not in flat-topped, corymbiform arrays) > 51
51 Plants rhizomatous (often colonial); heads in dense corymbiform or paniculiform arrays > 52
51 Plants usually taprooted or with caudices, sometimes also from spreading roots (stems single or clustered); heads usually borne singly, sometimes (2–5) in loose, corymbiform, cymiform, or paniculiform arrays, or in spiciform, racemiform, paniculiform, or corymbiform arrays, or glomerate (some Oönopsis) > 53
52 Stems and leaves sometimes stipitate-glandular or gland-dotted; heads in rounded, club-shaped, wand-shaped, or pyramid-shaped paniculiform (often secund) arrays, or in flat-topped, corymbiform arrays; involucres cylindric to campanulate, 3–12 mm, sometimes stipitate-glandular; phyllary midveins usually swollen, translucent, apices often with green zone, sometimes reflexed; rays 3–15(–21); disc corolla lobes lanceolate, erect to reflexed, style-branch appendages triangular; cypselae obconic, sometimes ± compressed, 5–8-nerved. Solidago
52 Stems and leaves stipitate-glandular; heads in dense, flat-topped, corymbiform arrays; involucres campanulate to hemispheric, 10–11 mm, stipitate-glandular; phyllary midveins not swollen, apices green-tipped and spreading-reflexed; rays 12–20; disc corolla lobes triangular, spreading, style-branch appendages linear; cypselae fusiform, distinctly compressed, 12–16-nerved (nerves whitish, raised; w United States) Oreochrysum
53 Heads usually in rounded, club-shaped, wand-shaped, or pyramid-shaped, paniculiform (often secund) arrays, or flat-topped, corymbiform arrays, or in spiciform, racemiform, or cymiform arrays, sometimes borne singly > 54
53 Heads borne singly or (2–15) in spiciform, racemiform, paniculiform, or corymbiform arrays > 55
54 Plants with caudices (stems clustered); leaves basal and cauline; heads in rounded, club-shaped, wand-shaped, or pyramid-shaped paniculiform (often secund) arrays, or flat-topped, corymbiform arrays; involucres campanulate to cylindric, 3–12 mm; phyllary midveins usually swollen and translucent; cypselae 5–8-nerved Solidago
54 Plants taprooted; leaves mostly cauline; heads usually in spiciform, racemiform, or cymiform arrays, sometimes borne singly; involucres campanulate, 11–13 mm; phyllary midveins not swollen; cypselae 4–5-nerved; California, Oregon Hazardia
55 Pappi brownish > 56
55 Pappi whitish or stramineous > 57
56 Stems and leaves glabrous or sparsely tomentose, eglandular; leaves basal (usually withering by flowering) and cauline, blades narrowly oblanceolate to lanceolate or linear, margins entire; heads borne singly, or (2–12) in glomerules or in loose, corymbiform arrays (subtended by little-reduced distal leaves); rays 6–25; cypselae prismatic or narrowly turbinate Oönopsis
56 Stems and leaves loosely tomentose to woolly, sometimes gland-dotted or stipitate-glandular; leaves basal (persistent) and cauline, basal blades oblanceolate to elliptic or linear, cauline lanceolate, margins entire, spinulose-dentate or -serrate, or shallowly laciniate; heads borne singly or (2–15, ± sessile) in racemiform, spiciform, or loose, corymbiform arrays (at ends of scapiform stems or peduncles); rays 10–80; cypselae subcylindric-fusiform Pyrrocoma
57 Plants 1–2 cm (± pulvinate), not mat-forming; leaves 1-nerved; heads ± sessile; phyllary margins ± scarious Townsendia
57 Plants 1–30(–60) cm, sometimes mat-forming; leaves 1–5-nerved; margins of outer phyllaries herbaceous (proximally indurate) > 58
58 Stems eglandular or stipitate-glandular, sometimes resinous; leaf margins entire, faces glabrous, scabrous, villous, or lanate, usually stipitate-glandular, sometimes eglandular; phyllaries unequal; rays 5–17; cypselae usually sericeous, sometimes glabrous Stenotus
58 Stems densely stipitate-glandular (viscid); leaf margins entire, toothed, or lobed, faces glabrous or scabrous, sometimes stipitate-glandular; phyllaries subequal (outer foliaceous); rays 11–23(–35); cypselae glabrous or villous Tonestus

Key to Genera of Group 11 Heads radiate; receptacles epaleate; pappi wholly, or partially, of awns or scales

1 Leaves and/or phyllaries dotted or streaked with pellucid (schizogenous) glands containing strong-scented oils > 2
1 Leaves and phyllaries rarely dotted or streaked (never with pellucid, schizogenous glands containing strong-scented oils, plants sometimes with sessile or stipitate, surface glands, sometimes strong-scented) > 8
2 Leaves opposite (blade margins proximally bristly-ciliate; ray florets borne on bases of subtending phyllaries; style branches of bisexual florets knob-like) Pectis
2 Leaves opposite or mostly alternate (blades often lobed, margins sometimes bristly-ciliate; ray florets borne on receptacles, not on bases of subtending phyllaries; style branches of bisexual florets linear) > 3
3 Phyllaries distinct to bases or nearly so > 4
3 Phyllaries ± connate 1/3–7/8+ their lengths (margins of outer sometimes distinct to bases) > 5
4 Rays yellow to orange (pappus scales multiaristate) Dyssodia
4 Rays whitish with pinkish or purplish stripes (pappi of scales plus bristles). Nicolletia
5 Calyculi 0; pappi of 2–5(–10) scales in ± 1 series (usually 0–5+ oblong to lanceolate, erose-truncate to laciniate, plus 0–2+, longer, subulate or aristate, some or all sometimes connate) Tagetes
5 Calyculi usually of (1–)5–8(–22) bractlets, rarely 0; pappi usually of 8–20 scales in 2 series (rarely coroniform) > 6
6 Bractlets of calyculi subulate or pectinate Dysodiopsis
6 Bractlets of calyculi deltate to subulate, not pectinate > 7
7 Plants (20–)30–70+ cm; involucres (7–18 ×) 5–12 mm; phyllaries weakly connate 1/3–2/3 their lengths Adenophyllum
7 Plants mostly (1–)5–30 cm; involucres (4–6 ×) 2–7 mm; phyllaries strongly connate 2/3–7/8 their lengths (margins of outer sometimes distinct to bases) Thymophylla
8 Leaves opposite, or proximal opposite (sometimes 2–3+ pairs) and distal alternate > 9
8 Leaves alternate > 24
9 Cypselae compressed or flattened, usually callous-margined and ± ciliate > 10
9 Cypselae (at least disc) mostly columnar or obpyramidal and 4–5-angled, or clavate, columnar, cylindric, or obconic and 10–15-ribbed (not both compressed and with ± ciliate margins) > 12
10 Phyllaries connate 2/3+ their lengths Lasthenia
10 Phyllaries distinct to bases > 11
11 Annuals, perennials, subshrubs, or shrubs, 2–45(–75) cm (usually glabrous or hairy other than woolly); leaves often lobed; involucres campanulate, cylindric, funnelform, or hemispheric, 3–15 mm diam.; disc florets 5–200+ Perityle
11 Annuals 1–3(–5) cm (woolly); involucres campanulate, 3–5 mm diam.; disc florets 7–12+ Eatonella
12 Disc cypselae mostly clavate, columnar, cylindric, or obconic and 10–15-ribbed > 13
12 Disc cypselae mostly columnar or obpyramidal and 4–5-angled (sometimes obovoid, smooth in Lasthenia; 2- or 4-angled in Monolopia) > 17
13 Heads in tight, corymbiform aggregations or arrays; rays 0, 1, or 3–5 > 14
13 Heads borne singly; rays 2–4 or 10–15 > 15
14 Rays 3–5; pappi of 5 erose scales alternating with 5 setiform scales or bristles (sometimes all 10 elements basally connate) Sartwellia
14 Rays 0 or 1; pappi of 2–4 hyaline scales Flaveria
15 Perennials; pappi of 1–5 scales Jaumea
15 Subshrubs or shrubs; pappi of 12–25, or ca. 50 scales > 16
16 Rays 10–15; pappi of 12–25 subulate scales in 1 series Clappia
16 Rays 2–4; pappi of ca. 50 setiform scales in 3–4 series Pseudoclappia
17 Ray laminae ca. 0.5 mm (inconspicuous); disc cypselae 2-angled (pappi of 2–7 scales) Monolopia
17 Ray laminae mostly 1–25+ mm (usually conspicuous) > 18
18 Disc corolla lobes lance-linear, lance-oblong, or linear (equal or unequal) > 19
18 Disc corolla lobes mostly deltate to lance-deltate or lance-ovate > 20
19 Disc corollas creamy to bright yellow Hymenothrix
19 Disc corollas pinkish, purplish, or whitish Palafoxia
20 Leaves usually sessile, sometimes petiolate; phyllaries distinct or partially connate (pappus scales not notably medially thickened) > 21
20 Leaves usually petiolate; phyllaries distinct (pappus scales usually notably medially thickened) > 22
21 Leaves opposite ± throughout, faces usually glabrous or glabrate (sparsely woolly to villous in L. minor and L. platycarpha) Lasthenia
21 Leaves opposite proximally, distal usually alternate, faces usu- ally densely to sparsely woolly Eriophyllum
22 Phyllaries 4–9(–12, margins often purplish or yellowish) Schkuhria
22 Phyllaries 6–18+ (margins rarely purplish, not yellowish) > 23
23 Annuals, biennials, or perennials, 10–80+ cm; leaves all or mostly opposite (if perennials, blades or lobes lanceolate to oblong, 2–20+ mm wide), or all or mostly alternate (proximal opposite) Bahia
23 Perennials, 3–20+ cm; leaves all or mostly opposite (blades or lobes lanceolate to lance-linear, mostly 1–8 mm wide). Picradeniopsis
24 Pappi partially of scales (scales subtended by, subtending, or alternating with bristles) > 25
24 Pappi wholly of scales (scales sometimes aristate, not associated with distinct bristles) > 37
25 Rays mostly white, sometimes wholly or partially blue, lilac, maroon, pink, purple, or violet > 26
25 Rays mostly yellow to orange, sometimes partially (rarely wholly) blue, brown, lilac, maroon, pink, purple, red, or violet > 31
26 Phyllary mid-nerves usually orange > 27
26 Phyllary mid-nerves not orange > 28
27 Plants not colonial (stems sometimes ± clustered); stems often stipitate-glandular; basal leaves persistent or withering by flowering; heads borne singly or (2–10) in corymbiform arrays; pappi usually of outer setae or scales plus 5–40(–50) inner bristles Erigeron
27 Plants colonial; stems eglandular; basal leaves withering by flowering; heads in corymbiform or diffuse, paniculiform arrays; pappi of 2–3 awns plus shorter bristles or scales, or wholly of minute scales Boltonia
28 Pappi of scales alternating with bristles > 29
28 Pappi of scales subtending bristles > 30
29 Phyllaries 10–50 in 2–6 series; disc florets 5–25 Chaetopappa
29 Phyllaries 10–14 in (1–)2 series; disc florets 28–40 Monoptilon
30 Leaf blades lance-elliptic, linear, oblong, or spatulate Ionactis
30 Leaf blades cordate-deltate to orbiculate or polygonally lobed (plants often persisting after cultivation) Pericallis
31 Pappi of (25–40) bristles subtending (8–15) subulate scales Grindelia
31 Pappi of scales (often setiform, inconspicuous) subtending bristles > 32
32 Heads borne singly or in 2s or 3s; phyllaries in 2–3(–4) series, usually 1- or 3-nerved (nerves golden-resinous), equal or subequal; cypselae 2-ribbed (each margin thickened, not resinous) Erigeron
32 Heads usually in corymbiform, ± paniculiform, or subumbelliform arrays, sometimes borne singly; phyllaries in 3–5 series, 1-nerved (nerves not golden-resinous), unequal to subequal; cypselae smooth or 1–14-nerved or -ribbed (nerves or ribs sometimes resinous) > 33
33 Leaves sessile, blades 3–11-parallel-nerved (nerves sunken), mostly lanceolate, linear, or ovate (often grasslike), margins entire, faces usually silky-sericeous, rarely glabrate; involucres turbinate Pityopsis
33 Leaves sessile or petiolate (basal), blades usually 1-nerved, mostly elliptic, elliptic-oblong, lance-linear, linear, oblanceolate, ovate, ovate-oblanceolate, or spatulate, margins entire, dentate, or serrate (sometimes ciliate), faces usually arachnose, hispid, pilose, strigose, or woolly, sometimes glabrate or glabrous; involucres campanulate, hemispheric, or turbinate > 34
34 Anthers tailed (leaf blades oblong to narrowly oblanceolate, 1–3 cm × 2–7 mm, bases clasping, margins entire, ± revolute; phyllaries lance-linear to linear, 3–5 mm, pilosulous; rays 10–30, laminae 1.5–2+ mm) Pulicaria
34 Anthers not tailed > 35
35 Plants proximally woolly, distally arachnose or pilose; basal leaves sessile Chrysopsis
35 Plants sparsely to ± densely hispid, strigose, or pilose; basal leaves petiolate > 36
36 Basal leaves: petioles ciliate; cauline leaves much reduced distally (bases not clasping); heads borne singly or in lax, paniculiform arrays; ray pappi of outer, setiform scales (0.3–1 mm) plus 20–35 inner bristles (3–6 mm) Bradburia
36 Basal leaves: petioles long-strigoso-ciliate; cauline leaves ± reduced distally (bases sometimes clasping or subclasping); heads usually in corymbiform, sometimes paniculiform, arrays, sometimes borne singly; ray pappi 0, or of outer, linear to linear-lanceolate or triangular scales (0.2–1 mm) plus 30–45 inner bristles (3–11 mm) Heterotheca
37 Styles (in bisexual, fertile florets) usually distally dilated and ± cylindric, style branches linear (sometimes adhering almost to minutely parted tips or essentially lacking, style-branch appendages essentially none; plants usually persisting after cultivation) > 38
37 Styles usually ± filiform (not distally dilated), style branches mostly lanceolate or linear (not adhering almost to tips, style-branch appendages either deltate, lanceolate, penicillate, or terete, or essentially none) > 40
38 Phyllaries connate 1/3–3/4 their lengths; ray laminae 5-nerved, 4-lobed or -toothed. Gazania
38 Phyllaries distinct; ray laminae 4-nerved, 3-lobed or -toothed > 39
39 Ray florets neuter, corollas adaxially yellow (sometimes drying bluish) or ± bluish; pappi of 7–8+ scales ca. 0.5 mm (usually hidden by cypsela hairs). Arctotheca
39 Ray florets pistillate, corollas adaxially whitish to purplish, or yellow to orange (then purple at bases); pappi (0 or) of 5–8 scales 0.5–4 mm (usually not hidden by cypsela hairs) Arctotis
40 Rays mostly white, sometimes wholly or partially blue, lilac, maroon, pink, purple, or violet > 41
40 Rays mostly yellow to orange, sometimes partially (rarely wholly) blue, brown, lilac, maroon, pink, purple, red, or violet > 53
41 Leaves (1–)2–3-pinnately lobed > 42
41 Leaves usually not lobed, sometimes 1-pinnately lobed > 43
42 Perennials; heads usually in lax to dense, corymbiform arrays, rarely borne singly Tanacetum
42 Annuals; heads borne singly or in open, corymbiform arrays Matricaria
43 Phyllaries mostly 5–13 in 1–2+ series; rays 5–8 > 44
43 Phyllaries (4–)13–80 in 2–7+ series; rays (1–)10–67 > 45
44 Biennials and perennials; pappus scales 12–18 Hymenopappus
44 Annuals; pappus scales 20–40 (setiform, basally coherent or connate, falling together or in groups) Syntrichopappus
45 Leaves all or mostly basal (blades linear, entire; heads borne singly; receptacles villous) Hulteniella
45 Leaves basal and cauline or mostly cauline > 46
46 Phyllaries usually 13 or 21 in (1–)2 series, subequal (leaf blades palmately nerved, cordate-deltate to orbiculate or polygonally lobed, margins dentate to denticulate, faces sparsely hairy; plants often persisting after cultivation) Pericallis
46 Phyllaries 4–80 in 2–7+ series, subequal to unequal > 47
47 Heads in corymbiform to paniculiform arrays (cypselae usu- ally strongly compressed, often winged) Boltonia
47 Heads usually borne singly (sometimes clusters of 3–6 in Gutierrezia) > 48
48 Cypselae ellipsoid, oblanceolate, obovate, or obovoid, strongly compressed to ± flattened (usually hairy, hair tips often glochidiform) > 49
48 Cypselae angular-columnar, or ± columnar, clavate, cylindric, or oblanceoloid, usually subterete, sometimes slightly compressed (sometimes with hair tips glochidiform) > 50
49 Cypsela margins sometimes thickened (not winglike); pappi of 12–35 lanceolate or subulate to setiform scales Townsendia
49 Cypsela margins sometimes ± winglike (wings glabrous); pappi of 2 barbellate awns Dichaetophora
50 Leaves oblanceolate to lance-linear, usually pinnati- fid, sometimes entire Aphanostephus
50 Leaves usually filiform, lanceolate, linear, oblanceolate, oblong, or spatulate, toothed or entire (margins sometimes ciliate) > 51
51 Shrubs (leaves mostly clustered distally on stems) Nipponanthemum
51 Annuals > 52
52 Plants 2–17 cm; leaves glabrous or sparsely pilose Pentachaeta
52 Plants 12–30 cm; leaves glabrous or minutely hairy, gland-dotted (glutinous) Gutierrezia
53 Ray corollas marcescent (usually becoming reflexed, dry, persisting past flowering) > 54
53 Ray corollas not marcescent (usually withering and falling after flowering) > 56
54 Heads usually in close corymbiform or glomerulate clusters; involucres mostly cam- panulate, cylindric, or obconic; rays 1–8; disc florets 5–25+ Psilostrophe
54 Heads borne singly; involucres campanulate, hemispheric, or rotate; rays 2–55; disc florets 10–250+ > 55
55 Leaves basal and cauline; blades lance-linear to broadly ovate, sometimes pinnately lobed or pinnatifid, faces usually floccose-woolly; phyllaries 8–13, or 21–34, in 2 series (abaxial faces floccose-tomentose); rays 5–7 or 20–55; disc florets 10–20 or 40–100+ Baileya
55 Leaves all basal, or basal-proximal, or basal and cauline; blades mostly oblanceolate to linear or filiform, sometimes lobed, faces glabrous or ± hairy, eglandular or ± gland-dotted; phyllaries 11–60+ in 3 series (abaxial faces ± hairy); rays 7–27; disc florets 20–250+ Tetraneuris
56 Leaves mostly 2–3-pinnately lobed > 57
56 Leaves usually not lobed, sometimes 3-lobed or 1-pinnately lobed (1–2-ternately lobed in some species of Bahia) > 58
57 Perennials; phyllaries (20–)30–60 in (2–)3–5+ series; rays 10–21+; disc florets 60–300+ Tanacetum
57 Subshrubs; phyllaries 8–16 in 2 series; rays 4–9; disc florets 10–25 Constancea
58 Disc florets functionally staminate (not producing fruits) > 59
58 Disc florets bisexual, fertile (producing fruits) > 62
59 Annuals; rays 5–15 > 60
59 Perennials or shrubs; rays 1–5 > 61
60 Phyllaries 12–15 in 1–2(–3) series Amphiachyris
60 Phyllaries 22–35 in 5–6 series Benitoa
61 Shrubs; disc florets 3–7; pappus scales 15–20 Amphipappus
61 Perennials; disc florets 6–15; pappus scales 2–6 Hymenoxys
62 Disc corollas often brown-purple to red-brown or tipped with brown-purple to red-brown (tubes much shorter than abruptly much-dilated, urceolate to campanulate throats, lobes often shaggily hairy, hairs ± moniliform) > 63
62 Disc corollas usually uniformly yellow to cream, sometimes purplish to reddish (tubes much shorter than to about equaling slightly dilated, funnelform to cylindric throats, lobes not shaggily hairy with moniliform hairs) > 64
63 Stems not winged (receptacles usually with setiform enations; style-branch apices ± attenuate) Gaillardia
63 Stems often winged (by decurrent leaf bases; receptacles rarely with setiform enations; style-branch apices penicillate or truncate) Helenium
64 Receptacles deeply pitted (each cypsela nested within a 5–6-sided cell) Balduina
64 Receptacles smooth or ± pitted (cypselae not nested within cells; outer disc florets rarely subtended by paleae in Amblyolepis) > 65
65 Phyllaries (7–)20–60 in 2–4+ series, mostly unequal (laminae of ray corollas usually coiling in age) > 66
65 Phyllaries 5–15(–40) in 1–2 series, mostly subequal to equal (laminae of ray corollas rarely coiling in age) > 71
66 Pappus scales 18–22 > 67
66 Pappus scales 4–12 > 68
67 Shrubs (20–40 cm); rays 5–14 Acamptopappus
67 Perennials (pulvinate, 1–2 cm); rays 13–21 Townsendia
68 Cypselae clavate to linear (compressed, lenticular in cross section), silky hairy; pappi of 4 quadrate to spatulate scales (leaves usually thinly lanate to densely woolly and/or gland-dotted, glandular-puberulent, glandular- villous, or stipitate-glandular) Hulsea
68 Cypselae clavate, cylindric, oblanceoloid, oblong, or ovoid, terete or compressed, usually (3–)5-ribbed, 5–8-nerved, or 4–6 sided, mostly glabrous or sparsely strigillose or strigose; pappi of 5–20 irregular or awn-like scales > 69
69 Leaf margins entire or spinulose toothed; cypselae terete or slightly compressed with rounded edges or 4–6-sided, without prominent nerves, glabrous or slightly strigose Xanthocephalum
69 Leaf margins entire; cypselae clavate, cylindric, oblanceoloid, oblong, or ovoid, sometimes compressed, usually (3–)5-ribbed or 5–8-nerved, mostly glabrous or sparsely strigillose or strigose > 70
70 Annuals; receptacles flat to convex (without hooked hairs); disc corollas 3- or 5-lobed; cypselae (3–)5-ribbed Pentachaeta
70 Annuals, perennials, or subshrubs; receptacles flat to conic (with hooked hairs); disc corollas 5-lobed; cypselae 5–8-nerved Gutierrezia
71 Pappus scales 30–40 (setiform, basally coherent or connate, falling together or in groups; annuals; leaves often 3-lobed near tips; ray laminae 3–5 mm) Syntrichopappus
71 Pappus scales 2–16 > 72
72 Cypselae stoutly obconic or obpyramidal (lengths usually 1–2, rarely to 3.5 times diams.) > 73
72 Cypselae narrowly clavate or columnar to obconic or obpyramidal (lengths usually 3+ times diams., if stouter, usually ± compressed) > 74
73 Annuals, biennials, or perennials; leaves all or mostly cauline (often 1– 2-terately lobed) Bahia
73 Perennials; leaves basal or basal and cauline (not lobed) Platyschkuhria
74 Phyllaries 17–21 in 2 series (inner hyaline, scalelike; herbage notably sweet scented) Amblyolepis
74 Phyllaries 8–12 in 2 series, or 6–40 in 2 series (inner herbaceous to scarious or scarious-margined; herbage not notably sweet-scented) > 75
75 Leaf blades sometimes pinnately lobed (lobes mostly filiform, linear, or oblong); phyllaries: outer connate or distinct, inner distinct Hymenoxys
75 Leaf blades (some or all) pinnately lobed (lobes mostly deltate to obovate); phyllaries: all basally connate Plateilema

Key to Genera of Group 12 Heads eradiate; receptacles epaleate; pappi none or nearly so

1 Leaves all or mostly opposite (distal sometimes alternate) > 2
1 Leaves alternate > 14
2 Corollas yellow > 3
2 Corollas mostly white, sometimes blue, lavender, pink, or purple > 8
3 Heads disciform (peripheral florets pistillate) Lasthenia
3 Heads discoid (florets all bisexual) > 4
4 Florets (5–)20–100+ per head (heads borne singly or in open arrays, not crowded in headlike or tight glomerules) > 5
4 Florets 1–5(–15) per head (heads often crowded in headlike or tight glomerules) > 6
5 Leaf blades usually lobed (mostly 5–30 mm); phyllaries 8–16 in 2–3 series, distinct Perityle
5 Leaf blades usually triangular-hastate to narrowly deltate, seldom notably lobed (30–120 mm); phyllaries 15–21 in 1(–2) series, wholly or partially connate Pericome
6 Leaves usually glabrous (often succulent) Flaveria
6 Leaves usually hispid, sericeous, strigose, villous, or woolly > 7
7 Shrubs Lagascea
7 Annuals Madia
8 Cypselae obcompressed or -obflattened (subtended by accrescent phyllaries, margins corky-winged, ± toothed) Dicoria
8 Cypselae mostly prismatic or columnar (if obcompressed, not subtended by accrescent phyllaries, margins not corky-winged and toothed) > 9
9 Style-branch appendages usually terete to clavate (lengths usually 2–5+ stigmatic lines) > 10
9 Style-branch appendages essentially none or deltate, lanceolate, linear, filiform, or penicillate (lengths mostly 0–3 times stigmatic lines) > 12
10 Florets 5(–6) Stevia
10 Florets 20–125 > 11
11 Plants 20–120 cm (terrestrial); involucres campanulate, 3–6 mm diam.; phyllaries usually 2-nerved Ageratum
11 Plants 10–30 cm (aquatic); involucres hemispheric or broader, 6–9 mm diam.; phyllaries not notably nerved Shinnersia
12 Anthers connate Perityle
12 Anthers distinct > 13
13 Heads in (bracteate) racemiform or spiciform arrays (1–2 per bract); pistillate florets usually 1–8+, rarely 0; functionally staminate florets 3–20+, corolla lobes soon reflexed Iva
13 Heads in (usually ebracteate) paniculiform arrays; pistillate florets 5; functionally staminate florets 5–10(–20+), corolla lobes erect Cyclachaena
14 Corollas mostly white, sometimes blue, lavender, pink, or purple > 15
14 Corollas mostly yellow (sometimes pale or reddish, or red-brown to purplish) > 21
15 Annuals > 16
15 Perennials, subshrubs, or shrubs > 17
16 Heads disciform (usually sessile); cypselae ± obovate to oblanceolate or oblong-cuneate, obcompressed or -obflattened (winged, usually producing apical spines) Soliva
16 Heads discoid (usually pedunculate); cypselae clavate to ± cylindric or compressed (obscurely 8–20-angled, not winged or with spines) Chaenactis
17 Phyllaries in 6+ series (apices often with ± dentate or fringed, linear to ovate appendages, sometimes spine-tipped) Centaurea
17 Phyllaries usually in 1–3 series (apices without appendages or spine tips) > 18
18 Style-branch appendages usually terete to clavate (lengths usually 2–5+ stigmatic lines) > 19
18 Style-branch appendages essentially none or deltate, lanceolate, linear, filiform, or penicillate (lengths mostly 0–3 times stigmatic lines) > 20
19 Phyllaries 5(–6) in ± 1 series; florets 5(–6) Stevia
19 Phyllaries 12–15 in 2–3 series; florets 7–10 Hartwrightia
20 Leaves basal and cauline, blades ovate to ± triangular (bases mostly truncate to cordate or hastate), margins coarsely dentate or lobulate to denticulate or entire (distalmost leaves often linear or scalelike); cypselae clavate to obovoid, faces distally stipitate-glandular Adenocaulon
20 Leaves mostly cauline, blades lanceolate to oblanceolate, margins laciniately pinnately lobed; cypselae pyriform, ± obcompressed, densely gland-dotted Leuciva
21 Leaf margins ± spiny (plants ± thistlelike; phyllaries: apical appendages prominently veiny, spiny-dentate or -lobed, spine-tipped) Carthamus
21 Leaf margins not spiny (plants not thistlelike; phyllary apices sometimes apiculate, not spine-tipped) > 22
22 Receptacles usually ± globose (leaves seldom lobed, stems usually winged by decurrent leaf bases) Helenium
22 Receptacles usually flat to convex (if ± conic, leaves usually 1–2-pinnately lobed, leaf bases not decurrent on stems) > 23
23 Heads disciform (peripheral florets pistillate) > 24
23 Heads discoid (all florets bisexual, fertile) > 28
24 Pistillate corollas lacking Cotula
24 Pistillate corollas ± tubular (distally 3–5-lobed or truncate) > 25
25 Heads usually in lax to dense, corymbiform arrays, rarely borne singly; involucres mostly hemispheric or broader, (3–)5–22+ mm diam.; phyllaries (20–)30–60+ in (2–)3–5+ series Tanacetum
25 Heads usually in paniculiform, racemiform, or spiciform arrays, sometimes in subcapitate clusters, sometimes borne singly; involucres hemispheric to campanulate, obconic, ovoid, or turbinate, 1.5–5(–12) mm diam.; phyllaries 5–20+ in 1–4(–7) series > 26
26 Heads borne singly or (2–20+) in usually corymbiform, rarely paniculiform, arrays or in subcapitate clusters; disc floret corollas bright yellow or ochroleucous (leaves usually gland- dotted) Sphaeromeria
26 Heads (usually 20–200+, 2–12+ in Picrothamnus) in paniculiform, racemiform, or spiciform arrays, rarely borne singly; disc floret corollas usually pale yellow, rarely red > 27
27 Subshrubs or shrubs (thorny); disc florets functionally staminate (corollas ± villous) Picrothamnus
27 Annuals, perennials, subshrubs, or shrubs (not thorny); disc florets bisexual and fertile, or functionally staminate (corollas usually glabrous, sometimes hairy, not villous) Artemisia
28 Subshrubs or shrubs > 29
28 Annuals or perennials > 32
29 Heads in paniculiform, racemiform, or spiciform arrays Artemisia
29 Heads borne singly or in loose, corymbiform arrays > 30
30 Phyllaries 5–6 in 1–2 series; florets 5–9 Tetradymia
30 Phyllaries 22–40 in 3–4+ series; florets (20–)40–100(–300+) > 31
31 Phyllaries 22–40 in 3–4+ series, deltate-ovate to elliptic or obovate; cypselae narrowly obovoid to oblong or elliptic, ± terete or flattened, ribs 5 (faces gland-dotted between ribs) Pentzia
31 Phyllaries 25–100+ in (3–)4–9+ series, mostly filiform, linear, or lanceolate; cypselae ellipsoid to obovoid, ± compressed, sometimes ± 3–4-angled (faces smooth, striate, ribbed, furrowed, or rugose, glabrous) Grindelia
32 Leaves 0–1-pinnately lobed > 33
32 Leaves 1–2-pinnately lobed > 34
33 Cypselae ± columnar to obovoid, ribs ± 10 (style-branch appendages rings of papillae or essentially 0) Leucanthemum
33 Cypselae ellipsoid to obovoid, ± compressed, sometimes ± 3–4-angled (style- branch appendages linear or lanceolate to ± deltate) Grindelia
34 Perennials Tanacetum
34 Annuals > 35
35 Phyllaries lance-triangular to ± ovate or elliptic (carinate); cypselae colum- nar to prismatic, ribs 4 Oncosiphon
35 Phyllaries oblong or ovate to spatulate or linear-spatulate (not carinate); cypselae obconic, slightly compressed, ribs 5 Matricaria

Key to Genera of Group 13 Heads eradiate; receptacles epaleate; pappi wholly of bristles

1 Leaves opposite (at least proximally) or whorled Group 13
1 Leaves alternate > 2
2 Phyllaries usually in 1–2 series and equal to subequal (sometimes coherent, often subtended by calyculi; in 2–4+ series and unequal in Lepidospartum, shrubs with leaves of flowering stems filiform to acerose or scalelike and pappi of ca. 150 bristles in 3–4 series) Group 13
2 Phyllaries usually in 3–10+ series and unequal, sometimes 1–2 series and subequal (distinct, calyculi 0) > 3
3 Corollas white, ochroleucous, or pink to purplish, sometimes red (then plants prickly- spiny) Group 13
3 Corollas cream or yellowish to yellow, orange, or brick-red (sometimes whitish, greenish, reddish, or purplish, or red-tipped) Group 13

Key to Genera of Group 13a

1 Corollas yellow to orange > 2
1 Corollas white, ochroleucous, or pink to purplish > 3
2 Leaves and phyllaries dotted or streaked with pellucid (schizogenous) glands contain- ing strong-scented oils Porophyllum
2 Leaves and/or phyllaries rarely dotted or streaked (never with pellucid, schizogenous glands, sometimes stipitate-glandular) Arnica
3 Involucres narrowly cylindric, (1–)2–3 mm diam.; phyllaries 4, or 5(–6) in ± 1–2 series; florets 4, or 5(–6) > 4
3 Involucres campanulate, cylindric, ellipsoid, hemispheric, or obconic, (2–)3–7(–25) mm diam.; phyllaries (5–)8–45(–65+) in (1–)2–8+ series; florets (3–)10–125(–200+) > 5
4 Subshrubs or shrubs; phyllaries 5(–6); florets 5(–6) Stevia
4 Vines; phyllaries 4; florets 4 Mikania
5 Cypselae 8–10-ribbed > 6
5 Cypselae (3–)4–5(–8)-ribbed > 7
6 Leaf blades deltate, lance-elliptic, lance-linear, lanceolate, lance-ovate, lance-rhombic, linear, oblong, obovate, ovate, rhombic-ovate, spatulate, suborbiculate, margins crenate, dentate, entire, laciniate-dentate, lobed, or serrate; style bases enlarged, hairy Brickellia
6 Leaf blades linear (distal sometimes scalelike), margins entire; style bases not enlarged, glabrous Asanthus
7 Pappi of 2–6+, coarsely barbellate bristles Trichocoronis
7 Pappi of (5–)10–80+, barbellulate, barbellate, or plumose bristles (or setiform scales) > 8
8 Involucres cylindric (3–4+ mm diam.); pappus bristles plumose (basally coherent or connate, falling together or in groups) Carminatia
8 Involucres usually obconic to hemispheric, sometimes campanulate, cylindric, or ellipsoid (2–7 mm diam.); pappus bristles smooth or barbellulate to barbellate (not plumose) > 9
9 Phyllaries ± equal > 10
9 Phyllaries unequal (outer shorter) > 13
10 Receptacles conic Conoclinium
10 Receptacles flat or convex > 11
11 Phyllaries 2- or 3-nerved, or not notably nerved, or pinnately nerved; style bases usually puberulent (glabrous in Eupatorium capillifolium); cypselae usually gland-dotted Eupatorium
11 Phyllaries 3-nerved, or 0- or 2-nerved; style bases glabrous; cypselae sometimes gland-dotted > 12
12 Involucres 2–3 mm diam.; phyllaries 7–16 in 1–2 series; florets 3–13 Koanophyllon
12 Involucres 3–6 mm diam.; phyllaries ca. 30 in 2–3 series; florets 10–60 Ageratina
13 Style bases usually puberulent (glabrous in Eupatorium capillifolium); cypselae usually glabrous and gland-dotted, sometimes scabrellous on ribs > 14
13 Style bases usually glabrous (hirsute in Flyriella); cypselae glabrous or hirsute, hirtellous, hispidulous, hispidulo-strigose, puberulent, or scabrellous (sometimes gland-dotted). > 15
14 Leaves mostly opposite (sometimes whorled, distal sometimes alternate) Eupatorium
14 Leaves mostly whorled (3–7 per node), rarely opposite Eutrochium
15 Annuals or perennials; involucres 2–5+ mm diam.; florets 10–30 > 16
15 Perennials, subshrubs, or shrubs; involucres (2–)4–7 mm diam.; florets (3–)25–50 > 17
16 Perennials, 20–60 cm (viscid); corollas white to ochroleucous, throats ± cylindric (± contracted distally, lengths 4–6 times diams.) Flyriella
16 Annuals or perennials, 30–120+ cm (not viscid, stems usually puberulent, hairs curled); corollas bluish, pinkish, purplish, or white, throats funnelform (not contracted distally, lengths 2.5–4 times diams.) Fleischmannia
17 Phyllaries usually readily falling, 18–65+ in 4–6+ series, 3–5-nerved; cypselae (3–)5- ribbed, scabrellous, usually gland-dotted Chromolaena
17 Phyllaries usually persistent, 7–35 in (1–)2–4 series, 2- or 4-nerved, 3-nerved, or obscurely nerved; cypselae 5(–7)-ribbed, hispidulous, hispidulo-strigose, puberulent, or sparsely scabrellous (sometimes gland-dotted) > 18
18 Phyllaries 2- or 4-nerved; corollas white to yellowish white; pappi readily falling or fragile Brickelliastrum
18 Phyllaries 3-nerved or obscurely nerved; corollas usually blue, lavender, or pinkish, sometimes white; pappi persistent > 19
19 Involucres 5–7 mm diam.; phyllaries 30–35; florets 30–50 Tamaulipa
19 Involucres 2–3 mm diam.; phyllaries 7–16; florets 3–13 Koanophyllon

Key to Genera of Group 13b

1 Heads disciform > 2
1 Heads discoid > 4
2 Leaf blades palmately or palmati-pinnately nerved, mostly deltate to ovate or orbiculate (plants polygamodioecious, stems of "staminate" plants wither soon after flower- ing, stems of "pistillate" plants elongate after flowering) Petasites
2 Leaf blades pinnately nerved, mostly ovate to lanceolate (sometimes pinnately lobed or dissected) > 3
3 Pistillate florets sometimes 1–3 in 1 series (Senecio mohavensis) Senecio
3 Pistillate florets 10–100+ in 1–3 series Erechtites
4 Subshrubs, shrubs (treelets), or vines > 5
4 Annuals, biennials, or perennials > 8
5 Vines (California, Oregon) Delairea
5 Subshrubs or shrubs (treelets) > 6
6 Phyllaries 4–6 in 1–2 series and equal or subequal; florets 4–9 Tetradymia
6 Phyllaries mostly 5, 8, 13, or 21 in (1–)2 series and equal or subequal, or 8–13 or 12–23+ in 2–4+ series and unequal (outer shorter); florets 3–80+ > 7
7 Phyllaries mostly 5, 8, 13, or 21 in (1–)2 series and equal or subequal Senecio
7 Phyllaries 8–23+ in 2–4+ series and unequal (leaves of flowering stems filiform to acerose or scalelike) Lepidospartum
8 Plants ± velutinous or villous (hairs purplish); style-branch appendages ± filiform (hispidulous, 1–2 mm; perennials, s Florida) Gynura
8 Plants rarely velutinous or villous (hairs rarely purplish); style-branch appendages essentially 0 (or deltoid to conic, mostly 0.1–1 mm; style-branch apices usually truncate-penicillate or truncate to rounded-truncate) > 9
9 Phyllaries (4–)5(–6; yellow; Wyoming) Yermo
9 Phyllaries (4–)5–30+ (usually green) > 10
10 Corollas usually yellow, sometimes orange-yellow or orange, rarely orange-red, purplish, or reddish > 11
10 Corollas usually white or ochroleucous to greenish or whitish, sometimes lavender, pinkish, or purplish > 16
11 Heads in racemiform or subthyrsiform arrays; phyllaries (4–)5(–8); florets (4–)5(–8). Rainiera
11 Heads usually in corymbiform, sometimes cymiform, racemiform, or subumbelliform, arrays or borne singly; phyllaries (5–)8–30+; florets (5–)20–80+ > 12
12 Calyculi usually of 1–8+ bractlets, sometimes 0; style-branch apices usually truncate-penicillate > 13
12 Calyculi 0; style-branch apices usually rounded-truncate or with deltoid to conic appendages > 14
13 Leaves basal and/or cauline (roots often fleshy and seldom branched and/or leaf margins with relatively many callous denticles) Senecio
13 Leaves basal and cauline (roots seldom fleshy, often branched; leaf margins with relatively few or no callous denticles) Packera
14 Involucres 3–8 mm diam.; florets 11–26 Luina
14 Involucres 7–15+ mm diam.; florets 20–80+ > 15
15 Leaf blades pinnately nerved, lanceolate, linear-oblanceolate, oblanceolate, ovate, or subrhombic Tephroseris
15 Leaf blades palmately nerved, ± reniform to orbiculate Cacaliopsis
16 Leaf blades palmately or palmati-pinnately nerved, mostly deltate to ovate or orbiculate (plants polygamodioecious, stems of "staminate" plants wither soon after flower- ing, stems of "pistillate" plants elongate after flowering) Petasites
16 Leaf blades palmately, palmati-pinnately, or pinnately nerved, mostly ovate, obovate, oblanceolate, or elliptic to lanceolate, lance-linear, or linear, sometimes cordate, deltate, hastate, reniform, or orbiculate (plants not polygamodioecious) > 17
17 Annuals Emilia
17 Perennials > 18
18 Phyllaries 5–8; florets 4–8 > 19
18 Phyllaries 7–21; florets 10–80+ > 21
19 Heads in racemiform to subpaniculiform arrays (Alaska) Parasenecio
19 Heads usually in corymbiform, sometimes paniculiform, arrays > 20
20 Basal and proximal cauline leaf blades ovate to elliptic (deeply 3–4-pinnatisect); calyculi of 1–3 bractlets (s Arizona, New Mexico) Psacalium
20 Basal and proximal cauline leaf blades mostly cordate, deltate, elliptic, hastate, ovate, or reniform, sometimes lanceolate or lance-linear (not 3–4-pinnatisect); calyculi 0 (e North America) Arnoglossum
21 Plants (50–)60–240 cm; calyculi of 4–9+ bractlets Hasteola
21 Plants 10–70 cm; calyculi 0 or of 1–5+ bractlets > 22
22 Leaf blades ovate to subrhombic (1–3 × 1–2 cm) Tephroseris
22 Leaf blades ovate to nearly cordate (5–15+ × 3–10+ cm) Rugelia

Key to Genera of Group 13c

1 Heads aggregated in second-order heads (florets 1 per individual head, each cluster subtended by ovate to orbiculate, prickly-margined bracts; subshrubs or shrubs) Hecastocleis
1 Heads borne singly or in corymbiform, paniculiform, or racemiform arrays (not aggregated in second-order heads; florets usually 3–300+ per individual head) > 2
2 Corollas usually 2-lipped (at least outer; inner sometimes nearly actinomorphic) > 3
2 Corollas actinomorphic (not two-lipped) > 5
3 Abaxial leaf faces glabrous or with scattered, straight, sometimes glandular, hairs and/or double hairs; cypselae not beaked Acourtia
3 Abaxial leaf faces usually tomentose, tomentulose, or covered with dense wool (thinly gray-tomentose in Leibnitzia); cypselae distally ± tapered or ± constricted into necks or beaks > 4
4 Heads chasmogamous (produced well after rosette leaves); cypselae glabrous or pubescent (hairs relatively short, apices rounded or apiculate) Chaptalia
4 Heads chasmogamous (early spring, produced before and concurrently with first rosette leaves) or cleistogamous (produced after rosette leaves); cypselae strigose to hispid (hairs relatively long, apices sharp-pointed) Leibnitzia
5 Plants often prickly-spiny and thistlelike and/or phyllary apices spinose or ± expanded into distinct, often fimbriate-fringed, pectinate, and/or prickly appendages > 6
5 Plants not prickly-spiny and thistlelike, phyllary apices not spinose or expanded and fringed > 19
6 Leaf margins spiny > 7
6 Leaf margins not spiny (tips sometimes ± spinose-apiculate) > 11
7 Stems winged > 8
7 Stems not or rarely winged (some Cirsium spp.) > 9
8 Receptacles not bristly (deeply pitted); cypsela attachments basal; pappus bristles basally connate Onopordum
8 Receptacles bristly (bearing setiform scales or "flattened bristles," not pitted); cypsela attachments slightly lateral; pappus bristles usually distinct, sometimes basally connate Carduus
9 Corollas ± purple; cypsela attachments lateral; pappi of distinct, minutely barbed (not plumose) flattened bristles ("setiform scales") Centaurea
9 Corollas white or purplish to red; cypsela attachments basal or oblique-basal; pappi of basally connate, plumose flattened bristles ("setiform scales") > 10
10 Involucres 35–100+ mm diam. (largest leaves 60–150 cm; receptacles becoming fleshy) Cynara
10 Involucres 10–50 mm diam. (largest leaves usually 20–50, sometimes to 110, cm; receptacles usually not notably fleshy) Cirsium
11 Heads disciform or radiant (peripheral florets usually neuter) > 12
11 Heads discoid (all florets bisexual and fertile) > 15
12 Heads disciform (phyllary appendages dentate or fringed, spiny or not; receptacles bearing setiform scales) Centaurea
12 Heads radiant > 13
13 Phyllary appendages 0 (biennials or perennials; spines on phyllary api- ces caducous) Mantisalca
13 Phyllary appendages present > 14
14 Annuals; leaf margins mostly entire or denticulate to serrulate; cypsela attachments oblique-basal; involucres 20–40 mm diam.; phyllary bodies linear, margins entire, appendages fimbriate; corollas of peripheral florets 30–70 mm Plectocephalus
14 Annuals, biennials, or perennials; leaf margins entire or toothed to pinnately lobed; involucres 10–25(–40) mm diam.; cypsela attachments lateral; phyllary bodies oblong to ovate or obovate, margins fimbriate, appendages fimbriate; corollas of peripheral florets 15– 30(–45) mm Centaurea
15 Cypsela attachments ± lateral > 16
15 Cypsela attachments basal > 17
16 Phyllary appendages dentate or fringed; pappi of persistent, nonplumose bristles Centaurea
16 Phyllary appendages entire or lacerate, not fringed; pappi of ± cadu- cous, distally plumose bristles Acroptilon
17 Phyllary apices spiny, hooked; pappi of distinct, nonplumose bristles. Arctium
17 Phyllary apices spiny or not, not hooked; pappi of basally connate, plumose flattened bristles ("setiform scales") > 18
18 Receptacles bristly (bearing setiform scales or "flattened bristles," becoming fleshy); florets 100–250+ Cynara
18 Receptacles not bristly (sometimes paleate, not fleshy); florets 10– 20 Saussurea
19 Phyllaries usually (12–30+) in 3–10+ series, wholly scarious or margins and/or apices notably scarious > 20
19 Phyllaries in 2–5+ series, ± herbaceous to chartaceous and/or margins and apices not notably scarious > 23
20 Annuals; pappi persistent; pappus bristles ± plumose Facelis
20 Annuals, biennials, or perennials; pappi readily falling; pappus bristles barbellate to barbellulate > 21
21 Heads in spiciform or subcapitate arrays or in glomerules in continuous or interrupted, usually spiciform, sometimes paniculiform, arrays (in terminal glomerules in depauperate plants); cypselae ± papillate (papillae myxogenic) or strigillose (hairs not myxogenic); pappus bristles usually basally connate, readily falling (in groups or rings; distinct in Omalotheca supina) Omalotheca
21 Heads usually in ± capitate clusters (subtended by leafy bracts) or corymbiform or paniculiform (often bracteate) arrays; cypselae usually glabrous or minutely hairy or papillate (papillae not myxogenic), sometimes minutely roughened and/or with 4–6 longitudinal ridges; pappus bristles distinct (falling separately) or basally coherent (falling in groups or rings) > 22
22 Involucres narrowly campanulate to cylindric; phyllaries mostly stramineous to brownish, sometimes purplish to pinkish (hyaline, stereomes not glandular) Euchiton
22 Involucres narrowly to broadly campanulate to cylindric; phyllaries white, rosy, tawny, or brown (opaque or hyaline, stereomes usually glandular). Gnaphalium
23 Style-branch appendages penicillate or essentially 0 (style branches stigmatic to tips) > 24
23 Style-branch appendages deltate to lanceolate or terete to clavate > 27
24 Heads discoid > 25
24 Heads disciform (peripheral pistillate florets in 1–10+ series) > 26
25 Subshrubs or shrubs; cypselae ± obpyramidal, obscurely ribbed Gochnatia
25 Perennials; cypselae columnar, sometimes arcuate, 8–10-ribbed Vernonia
26 Leaves all or mostly basal Sachsia
26 Leaves all or mostly cauline Pluchea
27 Style-branch appendages deltate to lanceolate > 28
27 Style-branch appendages terete to clavate (lengths usually 2–5+ stigmatic lines) > 31
28 Plants unisexual (florets unisexual), often glutinous (subshrubs or shrubs) Baccharis
28 Plants bisexual (some or all florets bisexual), sometimes glutinous (annuals or perennials) > 29
29 Perennials Brintonia
29 Annuals > 30
30 Plants (gracile) 2–14 cm; leaves linear to filiform, margins entire, abaxial faces glabrous or sparsely pilose; pappi of (3–)5 bristles. Pentachaeta
30 Plants (1–)2–100 cm; leaves ovate or obovate to lanceolate, linear, or subulate, margins entire, toothed, or pinnately lobed, abaxial faces glabrous or sparsely tomentose or woolly; pappi of 3–55 (sometimes basally connate) bristles Lessingia
31 Cypselae (3–)4–5(–8)-ribbed > 32
31 Cypselae 8–10-ribbed > 33
32 Pappi of (5–)10–80+ barbellulate, barbellate, or plumose bristles (or setiform scales) Tamaulipa
32 Pappi of 1–5 ± glandular setae Hartwrightia
33 Leaves mostly cauline (at flowering; mostly petiolate, sometimes sessile) Garberia
33 Leaves basal or basal and cauline (cauline mostly sessile) > 34
34 Heads usually in spiciform or racemiform, rarely corymbiform or thyrsiform, arrays; pappi of 12–40 coarsely barbellate to plumose bristles Liatris
34 Heads in corymbiform to paniculiform arrays; pappi of 35–40 barbellulate to barbellate (subequal) bristles Carphephorus

Key to Genera of Group 13d

1 Corollas all 2-lipped (shrubs) Trixis
1 Corollas actinomorphic > 2
2 Stems winged (heads in spiciform arrays; phyllaries 12–30+ in 3–6+ series, usually ± herbaceous to chartaceous, sometimes indurate, margins and/or apices seldom notably scarious; corollas yellowish) Pterocaulon
2 Stems not winged > 3
3 Phyllaries usually (12–30+) in 3–10+ series, scarious or margins and/or apices usually notably scarious, sometimes (3–10) in 1–2 series > 4
3 Phyllaries in 3–5+ series, usually ± herbaceous to chartaceous, sometimes indurate, margins and/or apices seldom notably scarious > 9
4 Heads usually discoid (unisexual or nearly so, staminate or pistillate; plants unisexual or nearly so; predominantly pistillate heads rarely with 1–9 central, functionally staminate florets; predominantly staminate heads rarely with 1–4+ peripheral, pistillate florets; involucres mostly 6–10 mm) > 5
4 Heads usually disciform (plants not unisexual; heads mostly alike, each with 4–200+ pistillate and 1–200+ bisexual or functionally staminate florets; heads rarely discoid in Xerochrysum, which has involucres 10–30 mm and brightly colored phyllaries in 3–8+ series) > 6
5 Plants (0.2–)4–25(–70) cm; basal leaves usually present at flowering (withering before in A. geyeri); pappus bristles (at least pistillate) usually basally connate or coherent Antennaria
5 Plants mostly 20–80(–120+) cm; basal leaves usually withering before flow- ering; pappus bristles distinct or basally connate Anaphalis
6 Pistillate florets fewer than bisexual > 7
6 Pistillate florets more numerous than bisexual > 8
7 Subshrubs; heads in glomerules in corymbiform arrays; involucres cam- panulate, 4–8 mm Helichrysum
7 Annuals, biennials, or perennials; heads borne singly or (2–3) in loose, corymbiform arrays; involucres ± hemispheric, 10–30 mm Xerochrysum
8 Heads usually in glomerules in corymbiform or paniculiform arrays, sometimes in terminal clusters; cypselae usually glabrous, sometimes with papilliform hairs (hairs not myxogenic), sometimes minutely roughened and/or with 4–6 longitudinal ridges; pappus bristles usually distinct (falling separately), sometimes basally coherent (falling in groups or rings) Pseudognaphalium
8 Heads usually in glomerules in continuous or interrupted, usually spiciform, sometimes paniculiform, arrays (in terminal glomerules in depauperate plants); cypselae ± papillate (papilliform hairs myxogenic); pappus bristles basally connate, readily falling (in rings) Gamochaeta
9 Leaves and/or phyllaries dotted or streaked with pellucid (schizogenous) glands containing strong-scented oils Porophyllum
9 Leaves and/or phyllaries rarely dotted or streaked (never with pellucid, schizogenous glands containing strong-scented oils, plants sometimes with sessile or stipitate, surface glands and strong-scented) > 10
10 Subshrubs, shrubs, or treelets > 11
10 Annuals, biennials, or perennials > 25
11 Plants unisexual (florets unisexual), often glutinous Baccharis
11 Plants bisexual (some or all florets bisexual), sometimes glutinous, gland-dotted, or stipitate-glandular > 12
12 Phyllaries disposed in vertical ranks and unequal > 13
12 Phyllaries disposed in spirals and equal or unequal > 16
13 Leaves basal and cauline, blades 3-nerved; heads in glomerate clusters grouped in flat-topped, corymbiform arrays; phyllaries yellowish, some- times distally green Bigelowia
13 Leaves cauline, blades 1-nerved (sometimes with 1–2 fainter lateral pairs); heads (sometimes clustered) in paniculiform, corymbiform, or cymiform arrays, or borne singly; phyllaries stramineous, tan, or green, distally green or purplish > 14
14 Leaf faces gland-dotted (in pits); heads in dense, cymiform arrays Chrysoma
14 Leaf faces gland-dotted (sessile) or stipitate glandular; heads borne singly or in condensed, cymiform clusters, grouped in paniculiform or corymbiform arrays, or in congested, cymiform to corymbiform arrays > 15
15 Heads in congested, cymiform to corymbiform arrays; disc florets 4–15; cypselae oblong to obconic Lorandersonia
15 Heads borne singly or in condensed, cymiform clusters grouped in paniculiform or corymbiform arrays; disc florets (2–)5–6 (–40); cypselae subcylindric Chrysothamnus
16 Shrubs or treelets > 17
16 Subshrubs > 21
17 Heads borne singly; pappi of 30–60 bristles subtending 15–20 subulate-aristate scales, or of ca. 120 bristles Peucephyllum
17 Heads sometimes borne singly, sometimes in clusters or glomerate, usually in spiciform, racemiform, paniculiform, cymiform, or corymbiform arrays; pappi of 15–60 bristles (ca. 150 bristles in 3–4 series in 238 Lepidospartum, in part, shrubs with leaves of flowering stems filiform or acerose to scalelike). > 18
18 Plants spinescent; heads (2–4) in glomerate clusters, these grouped in corymbiform arrays; pappi of 15–20 (flattened) bristles Amphipappus
18 Plants not spinescent; heads sometimes borne singly, sometimes in clusters (not glomerate), usually in spiciform, racemiform, paniculiform, cymiform, or corymbiform arrays; pappi of 20–60 bristles > 19
19 Stems not resinous; leaves entire or toothed (teeth sometimes bristly); heads usually in spiciform, racemiform, narrowly paniculiform, or corymbiform arrays, rarely borne singly; phyllaries not resinous; pappi reddish brown. Hazardia
19 Stems resinous; leaves entire; heads borne singly or in clusters (at branch tips), and/or in usually cymiform or racemiform, sometimes paniculiform or thyrsiform arrays; phyllaries resinous; pappi whitish tan to reddish > 20
20 Leaves filiform, linear, lanceolate, or spatulate (adaxially sulcate, concave or plane), margins sometimes undulate or crisped; heads borne singly or in usually cymiform or racemiform, sometimes paniculiform or thyrsiform, arrays; involucres hemispheric or obconic; disc florets 4–70, corolla lobes equal (cypselae 2–10 mm) Ericameria
20 Leaves filiform, margins flat or involute; heads in clusters at branch tips, grouped in cymiform or racemiform arrays; involucres turbinate; disc florets 3–7, corolla lobes unequal (cypselae 1–3 mm) Gundlachia
21 Stems eglandular; leaves entire > 22
21 Stems gland-dotted or stipitate-glandular; leaves entire, toothed, or pinnatifid > 23
22 Heads borne singly or in cymiform-racemiform arrays; involucres 11–15(–17) mm; florets 4–7; cypselae oblong, 5–6-ribbed, glabrous Cuniculotinus
22 Heads borne singly or in cymiform arrays; involucres 5–7 mm; florets 12–25+; cypselae narrowly oblong, 8–13-nerved (per face), ± sericeous Arida
23 Heads borne singly (at tips of branches) or in corymbiform arrays; cypselae dimor- phic (ray ± 3-sided, disc compressed) Xanthisma
23 Heads usually in spiciform, racemiform, corymbiform, or cymiform arrays, rarely borne singly; cypselae monomorphic (terete, subterete, or compressed) > 24
24 Basal leaves persistent; heads in compact clusters grouped in corymbiform arrays; involucres 3–9.5 mm; disc corollas goblet-shaped (tubes elongating at flowering, elevating throats beyond involucres); cypselae obpyramidal, 5–11- ribbed (ribs sometimes thick and resinous), sericeous Isocoma
24 Basal leaves withering by flowering; heads in spiciform, racemiform, or cymiform arrays; involucres 11–13 mm; disc corollas ± tubular (tubes not elevating throats); cypselae fusiform to deltoid, 4–5-nerved, glabrous Hazardia
25 Annuals or biennials > 26
25 Perennials > 33
26 Heads usually discoid (sometimes radiant in Lessingia) > 27
26 Heads usually disciform > 29
27 Leaf blades rounded-deltate, reniform, rounded-rhombic, or suborbiculate, margins toothed or entire, faces usually lanate, pilose, or tomentose, sometimes glandular-pubescent and/or furfuraceous as well; pappi of 35–150 bristles in 1–4 series Psathyrotes
27 Leaf blades ovate, obovate, oblong, lanceolate, oblanceolate, or linear, faces glabrous, canescent, or puberulent, abaxial glabrous or sparsely tomentose to woolly, sometimes stipitate-glandular as well; pappi of 3–55 bristles in 1–3 series > 28
28 Leaf adaxial faces glabrous, puberulent, or canescent; involucres turbinate; phyllaries usually spreading to reflexed, rarely appressed; corollas yellow (limbs of peripheral florets not expanded); pappus bristles white to tawny, distinct Dieteria
28 Leaf adaxial faces sparsely tomentose to woolly; involucres hemispheric, obconic, campanulate, or narrowly cylindric; phyllaries erect or recurved; corollas (white, pink, lavender, or) yellow (limbs of peripheral florets frequently palmately expanded, heads ± radiant); pappus bristles tan to reddish, distinct or connate Lessingia
29 Annuals (eglandular); disc corollas without prominent orange veins, style appendages lanceolate or linear > 30
29 Annuals or biennials (usually gland-dotted or stipitate-glandular, sometimes eglandular, in Conyza); disc corollas sometimes with prominent orange veins (Erigeron), style appendages deltate > 31
30 Heads borne singly; peripheral pistillate (or reduced ray) florets in 1 series; pappi (0 or) of (3–)5 bristles (or subulate scales, not surpassing corollas at flowering) Pentachaeta
30 Heads in paniculiform arrays (borne singly in small plants); peripheral pistillate florets in 2–5+ series; pappi of (20–)25–40(–55) bristles (surpassing corollas at flowering) Symphyotrichum
31 Biennials; stems ascending; heads borne singly (at ends of branches); disc corolla throats somewhat inflated (white-indurate); pappi of outer, shorter setae plus 15–20 inner, barbellate bristles Erigeron
31 Annuals; stems erect; heads usually in corymbiform, paniculiform or racemiform arrays, rarely borne singly; disc corollas narrowly funnelform (throats neither inflated nor indurate); pappi of 10–30 barbellate bristles > 32
32 Leaf faces often stipitate-glandular or gland-dotted; phyllaries lacking orange to brown midnerves; cypselae densely sericeous, ± strigillose, or glabrous, often stipitate-glandular and/or gland-dotted Laënnecia
32 Leaf faces eglandular; phyllaries with orange to brownish midnerves; cypselae glabrous or strigillose, eglandular Conyza
33 Heads disciform > 34
33 Heads discoid > 36
34 Cauline leaf margins entire or spinulose-serrate; heads borne singly or 2–3 in ± ± corymbiform arrays; cypselae subcylindric-fusiform, 3–4-angled, ± compressed, with 10–12 faint nerves; pappi of 15–60, rigid, unequal, smooth bristles in 1 series Pyrrocoma
34 Cauline leaf margins entire, dentate, or pinnatifid (lobed); heads in corymbiform arrays; cypselae oblong or oblong-obovoid to elliptic or obovoid, ± compressed or flattened, 2(–4)-nerved or ± nerved on edges; pappi of outer setae or scales plus 5–40 bristles, or of 30–40+ bristles in 2 series (outer usually shorter) > 35
35 Plants ± densely white-tomentose (at least some surfaces); phyllaries 1-nerved (nerves not golden-resinous); disc corollas yellowish, throats narrowly funnelform, not indurate (nerves pale, not resinous); pappi of 30–40+ bristles in 2 series (outer bristles usually shorter) Laënnecia
35 Plants ± hirsute or pilose; phyllaries usually 1–3-nerved (nerves golden-resinous); disc corollas yellow, strongly constricted basally, throats sometimes strongly inflated-indurate (nerves often orange-resinous); pappi of outer setae plus 7–25 inner bristles or of 7–25 bristles Erigeron
36 Style-branch appendages usually abaxially and adaxially papillate to hispidulous > 37
36 Style-branch appendages glabrous adaxially > 38
37 Stems erect; heads borne singly or in corymbiform arrays; cypselae narrowly obconic; pappi of 70–90, distinct bristles Psathyrotopsis
37 Stems erect or spreading; heads borne singly; cypselae cylindro-fusiform to obpyramidal; pappi of 35–150, distinct or basally connate bristles Psathyrotes
38 Phyllary midnerves translucent and swollen (at least basally, not resinous) Solidago
38 Phyllary midnerves usually not notably swollen (orange-resinous in Erigeron) > 39
39 Phyllary and corolla nerves orange-resinous; pappi of outer, shorter setae or scales plus inner, longer bristles Erigeron
39 Phyllary and corolla nerves not orange-resinous, or only corolla nerves orange-resinous; pappi of equal or unequal bristles > 40
40 Phyllaries subequal, foliaceous Toiyabea
40 Phyllaries usually unequal (sometimes subequal, then outer not foliaceous), outer ± herbaceous (sometimes foliaceous), or chartaceous, or proximally indurate > 41
41 Phyllaries keeled, distally with relatively small green zones or green along midveins; pappus bristles in 2–3 series (outer notably shorter or relatively few) > 42
41 Phyllaries usually flat, sometimes keeled, distally herbaceous or green; pappi of equal or unequal bristles in 1–3 series (outer not notably shorter) > 43
42 Leaves cauline (proximal withering by flowering), margins without coarse spreading cilia near bases; phyllary margins often reddish, sometimes hyaline, abaxial faces glabrous or glabrate to woolly, sometimes stipitate-glandular Eucephalus
42 Leaves basal and cauline (basal and proximal withering by flowering), margins with coarse spreading cilia near bases or on petioles; phyllary margins not reddish, scarious, abaxial faces ± hispid or stipitate-glandular Heterotheca
43 Leaf faces densely scabrous and short-stipitate-glandular; phyllaries ± keeled proximally (Esmeralda County, Nevada) Tonestus
43 Leaf faces glabrous or canescent, ± puberulent, hispidulous, tomentose, or villous, and/or sometimes ± stipitate-glandular or gland-dotted; phyllaries sometimes keeled > 44
44 Leaves basal and cauline, basal and proximal petiolate, distal sessile; style-branch appendages lanceolate > 45
44 Leaves cauline, sessile; style-branch appendages triangular > 46
45 Plants densely stipitate-glandular, with caudices; stems densely clustered, simple; leaf blades obovate or oblong to broadly oblanceolate; phyllaries keeled; disc corolla throats cylindric; cypselae white strigoso-hirsute Triniteurybia
45 Plants sparsely, if at all, stipitate-glandular, taprooted; stems single, usually branched; leaf blades lanceolate to oblanceolate; phyllaries flat; disc corolla throats funnelform; cypselae sparsely appressed-hairy Dieteria
46 Phyllary margins scarious; disc corolla lobes unequal; cypselae obpyramidal, sericeous; pappi of 40–50 tawny bristles Isocoma
46 Phyllary margins not scarious; disc corolla lobes equal; cypselae prismatic, narrowly turbinate, fusiform, or deltoid, glabrous or sparsely scabrous; pappi of 15–30 reddish brown to brownish bristles > 47
47 Stems glabrous or scabrous, eglandular; leaf bases not subclasping, margins entire; cypselae prismatic or narrowly turbinate; pappus bristles barbellate Oönopsis
47 Stems scabrous to sparsely tomentulose, distally stipitate-glandular; leaf bases subclasping, margins serrate; cypselae fusiform to deltoid; pappus bristles smooth Hazardia

Key to Genera of Group 14 Heads eradiate; receptacles epaleate; pappi wholly, or partially, of awns or scales

1 Florets 1(–2) or (1–)2–4(–5+) per head and heads in second-order heads or in headlike clusters > 2
1 Florets (2–)10–100(–1000) per head and heads borne singly or in usually corymbiform, paniculiform, racemiform, or spiciform arrays (heads ± crowded in Orochaenactis, annuals with pappi of 11–17 basally connate, oblanceolate scales, and in Eriophyllum mohavense, annuals with pappi of 12–14 distinct, linear to spatulate scales) > 7
2 Subshrubs or shrubs > 3
2 Annuals or perennials > 4
3 Leaves alternate, blades narrowly lance-linear, margins serrate (± thickened, spiny near bases); corollas purplish Hecastocleis
3 Leaves opposite, blades lance-ovate to ovate, margins ± serrate (not notably thick- ened or spiny); corollas yellow Lagascea
4 Annuals, 1–5 cm; leaves opposite (basal and cauline, crowded, seemingly whorled) Dimeresia
4 Perennials, mostly 10–200 cm; leaves alternate (basal or basal and cauline, basal usually crowded) > 5
5 Plants mostly 100–200 cm (thistlelike); leaf blades 1–3-pinnately lobed, ultimate margins toothed (prickly or spiny) Echinops
5 Plants mostly 10–120 cm (not thistlelike); leaf blades not lobed, margins usually toothed, rarely entire (not prickly or spiny) > 6
6 Heads (1–)10–40 per cluster, each cluster subtended by (2–)3, ± deltate bracts; pappi of 5(–6), 1-aristate scales (look closely for squamiform, gradually to abruptly tapering base of each arista), no scales tipped with plicate aristae Elephantopus
6 Heads 1–5+ per cluster, each cluster subtended by 1–2, lanceolate to spatulate or linear bracts; pappi of 6–10, ± laciniate to aristate scales, 2(–3+) of the aristate scales each with its awnlike arista plicate (2-folded) distally Pseudelephantopus
7 Leaves opposite (at least proximal, cauline sometimes mostly alternate) or whorled > 8
7 Leaves alternate > 27
8 Corollas mostly yellow (sometimes with purple, red, or red-brown) > 9
8 Corollas mostly white to cream or blue, lavender, pink, or purple > 17
9 Leaves and/or phyllaries dotted or streaked with pellucid (schizogenous) glands containing strong-scented oils Tagetes
9 Leaves and/or phyllaries rarely dotted or streaked (never with pellucid, schizogenous glands containing strong-scented oils, plants sometimes with sessile or stipitate, surface glands and sometimes otherwise strong-scented) > 10
10 Phyllaries often ± conduplicate and navicular; disc corollas usually 4-lobed; cypselae strongly flattened or weakly 3–4-angled, usually callous-margined, often ciliate > 11
10 Phyllaries usually flat to weakly navicular (none in Carlquistia in which receptacular paleae function as an involucre); disc corollas (4–)5-lobed; cypselae usually obpyramidal to obconic, sometimes columnar, seldom clavate or cylindric, often 4–5-angled (seldom strongly compressed or flattened, callous-margined, and ciliate) > 12
11 Leaf blades usually lobed (mostly 5–30 mm); phyllaries 8–16 in 2–3 series, distinct Perityle
11 Leaf blades usually triangular-hastate to narrowly deltate, seldom notably lobed (30–120 mm); phyllaries 15–21 in 1(–2) series, wholly or partially connate Pericome
12 Pappus scales (9–17) subulate, plumose Carlquistia
12 Pappus scales not both subulate and plumose > 13
13 Leaves usually sessile, sometimes obscurely petiolate (rarely truly petiolate); pappus scales not notably medially thickened > 14
13 Leaves usually petiolate; pappus scales usually notably medially thickened > 15
14 Leaves glabrous (often granular-glandular, not woolly) Amblyopappus
14 Leaves ± woolly or tomentose (usually stems and/or phyllaries as well) Eriophyllum
15 Annuals; leaves all or mostly opposite; pappus scales 8+ Schkuhria
15 Annuals or biennials; leaves proximally opposite, mostly alternate; pappus scales 11–18 > 16
16 Leaves lobed (lobes linear, 1–2 mm wide); disc corolla lobes lance-linear, lance-oblong, or linear (lengths mostly 2+ times widths); pappus scales distinct, narrowly lanceolate to subulate, some or all ± aristate Hymenothrix
16 Leaves lance-oblong to linear (not lobed); disc corolla lobes mostly deltate, lance-deltate, lanceolate, or ovate (lengths mostly 1–2 times widths); pappus scales basally connate (falling together), oblanceolate, obtuse Orochaenactis
17 Style-branch appendages essentially 0 or ± penicillate or deltate to lanceolate, linear, or filiform (lengths mostly 0–3+ times lengths of stigmatic areas or lines) > 18
17 Style-branch appendages usually terete to clavate (lengths usually 2–5+ times lengths of stigmatic lines) > 20
18 Phyllaries often ± conduplicate and navicular; disc corollas usually 4-lobed; cypselae strongly flattened or weakly 3–4-angled, usually callous-margined, often ciliate Perityle
18 Phyllaries usually flat to weakly navicular; disc corollas 5-lobed; cypselae obpyramidal, 4-angled (not callous-margined and ciliate) > 19
19 Leaf blades broadly lanceolate to linear (not lobed); corollas usually pinkish or purplish, sometimes whitish; cypselae densely to sparsely hairy (hairs straight) Palafoxia
19 Leaf blades (at least mid-cauline) 3- or 5-lobed or -foliolate (blades or leaflets broadly to narrowly oblong to ovate); corollas whitish; cypselae sparsely hairy (hairs curled) Florestina
20 Involucres narrowly cylindric, (1–)2–3 mm diam.; phyllaries 5(–6) in ± 1– 2 series; florets 5(–6) Stevia
20 Involucres campanulate, cylindric, ellipsoid, hemispheric, or obconic, (2–)3–7(–25) mm diam.; phyllaries (5–)8–45(–65+) in (1–)2–8+ series; florets (3–)10–125(–200+) > 21
21 Cypselae 8–10-ribbed (pappi of 1–5+ muticous, erose, lacerate, or lanceolate to subulate scales plus 9–12+ aristate scales) Carphochaete
21 Cypselae (3–)4–5(–8)-ribbed > 22
22 Pappi of 8–13 plumose, setiform scales (coherent or ± connate, falling together or in groups) Carminatia
22 Pappi usually of 2–6(–12) muticous or aristate to subulate scales plus 0–6(–12) setiform scales, rarely coroniform (Ageratum) > 23
23 Phyllaries unequal; receptacles flat to convex (not warty) > 24
23 Phyllaries ± equal; receptacles convex to conic or hemispheric (sometimes warty) > 25
24 Leaves mostly sessile (or nearly so), blades linear; cypselae ± fusiform Malperia
24 Leaves petiolate, blades ovate, deltate, or rhombic to lanceolate; cypselae prismatic Pleurocoronis
25 Leaves whorled (4 or 6 per node), blades linear; heads borne singly (plants ± aquatic) Sclerolepis
25 Leaves mostly opposite (distal sometimes alternate), blades elliptic, lanceolate, or oblong; heads usually in cymiform to corymbiform arrays, sometimes borne singly > 26
26 Leaves petiolate; involucres 3–6 mm diam.; phyllaries usually 2-nerved; pappi usually of 5–6 aristate scales, rarely coroniform Ageratum
26 Leaves sessile; involucres 3–4(–5) mm diam.; phyllaries obscurely 3–4-nerved; pappi of 2–6 setiform scales. Trichocoronis
27 Leaf margins prickly to spiny (plants ± thistlelike) > 28
27 Leaf margins not prickly or spiny (tips sometimes spinose or apiculate; plants not thistlelike) > 34
28 Stems winged > 29
28 Stems not or rarely winged (some Cirsium spp.) > 30
29 Cypsela attachments basal; pappus scales basally connate Onopordum
29 Cypsela attachments slightly lateral; pappus scales usually distinct, sometimes basally connate Carduus
30 Leaves variegated (with white veins or mottlings; stamen filaments connate). Silybum
30 Leaves not variegated (stamen filaments distinct) > 31
31 Corollas white or purplish to red; cypsela attachments basal; pappi of basally connate, plumose, setiform scales ("flattened bristles") > 32
31 Corollas yellow to orange, red, or ± purple; cypsela attachments lateral; pappi 0 or of distinct, barbellulate, setiform scales ("flattened bristles") or subulate scales > 33
32 Involucres 35–100+ mm diam. (larger leaves 60–150 cm; receptacles becoming fleshy) Cynara
32 Involucres 10–50 mm diam. (larger leaves usually 20–50, sometimes to 110 cm; receptacles usually not notably fleshy) Cirsium
33 Heads discoid (all florets bisexual, fertile); cypselae 4-angled Carthamus
33 Heads disciform (peripheral florets neuter); cypselae terete, 20-ribbed Centaurea
34 Corollas mostly white or blue, lavender, pink, or purple > 35
34 Corollas mostly yellow to orange (sometimes with purple, red, or red-brown) > 53
35 Anthers tailed (styles swollen or with rings of hairs proximal to branches) > 36
35 Anthers not tailed (sometimes sagittate; styles not swollen or with rings of hairs proximal to branches) > 44
36 Heads discoid (all florets bisexual and fertile) > 37
36 Heads disciform or radiant (peripheral florets usually neuter) > 39
37 Cypsela attachments basal (receptacles becoming fleshy; florets 100–250+; pappus scales basally connate) Cynara
37 Cypsela attachments ± lateral > 38
38 Phyllary appendages dentate or fringed (often spiny); pappi of persis- tent, nonplumose scales Centaurea
38 Phyllary appendages entire or lacerate, not fringed; pappi of readily falling, distally plumose bristles Acroptilon
39 Heads disciform > 40
39 Heads radiant > 41
40 Phyllary appendages dentate or fringed, often spiny Centaurea
40 Phyllary appendages none (apices acute, entire) Crupina
41 Phyllary appendages none (apices spiny) > 42
41 Phyllary appendages present > 43
42 Biennials or perennials; spines on phyllary apices soon falling; cypsela apices not coronate Mantisalca
42 Annuals; spines on phyllary apices persistent; cypsela apices coronate Volutaria
43 Cypselae compressed (oblong; attachment scars rimmed, rims whitish, swollen), apices denticulate Amberboa
43 Cypselae ± terete (barrel-shaped; attachment scars not rimmed), apices entire Centaurea
44 Phyllaries 18–70+ in 3–8+ series > 45
44 Phyllaries 5–15(–21) in 1–2(–3) series > 48
45 Heads pseudo-radiant or -radiate (corollas of peripheral, bisexual florets enlarged, zygomorphic); phyllary margins (at least of the outer), pectinately spinose-toothed Stokesia
45 Heads discoid; phyllary margins not pectinately spinose-toothed > 46
46 Annuals (perhaps persisting); cypselae not ribbed Cyanthillium
46 Perennials (sometimes functionally annuals); cypselae 8–10-ribbed > 47
47 Heads each subtended by 3–8+, ± foliaceous bracts; pappi readily falling Centratherum
47 Heads not each subtended by foliaceous bracts; pappi persistent Vernonia
48 Style-branch appendages usually terete to clavate (lengths usually 2–5+ times lengths of stigmatic lines) > 49
48 Style-branch appendages mostly deltate to lanceolate, linear, or filiform, sometimes essentially none (lengths mostly 0–3+ times lengths of stigmatic areas or lines) > 50
49 Phyllaries 5(–6) in 1 series; florets 5(–6) Stevia
49 Phyllaries 12–15 in 2–3 series; florets 7–10 Hartwrightia
50 Heads in (usually secund) spiciform arrays; florets 3 Thurovia
50 Heads borne singly or in corymbiform or cymiform arrays; florets 8–70 > 51
51 Cypselae stoutly obconic to obpyramidal, usually 4-angled and 12–16-ribbed (lengths usually 1–2, rarely to 3.5 times diams.; phyllary margins usually notably membranous to scarious) Hymenopappus
51 Cypselae narrowly clavate to cylindric or compressed, obscurely 8–20-angled, or ± quadrangular with 8–12 obscure nerves (lengths usually 3+ times diams., if stouter, usually ± compressed; phyllary margins not notably membranous or scarious) > 52
52 Leaves mostly basal; heads borne singly; florets 10–30+ (perennials 2–9 cm, 10–20+ cm across; leaf blades 1- or 3-nerved, cordate, elliptic, ovate, or rounded, margins entire or distally ± crenate, revolute to ± plane, faces ± strigose and gland-dotted, adaxial sometimes glabrescent) Chamaechaenactis
52 Leaves basal and cauline or mostly cauline; heads borne singly or in ± cymiform arrays; florets 8–70+ Chaenactis
53 Shrubs; pappi of 12–30 scales (sometimes with bristles as well) > 54
53 Annuals, biennials, perennials, subshrubs, or shrubs; pappi mostly of 1–12(–20+) scales (scales sometimes subtending 20–100+ bristles; if shrubs, pappus scales 1 or 3–5) > 58
54 Phyllaries 4–6, or 8–18, in 2 series, ± equal > 55
54 Phyllaries 7–60+ in 3–5 series, mostly unequal > 56
55 Florets 4–8 (cypselae copiously pilose, hairs white, 4–14 mm, sometimes obscuring pappi) Tetradymia
55 Florets 12–21 (cypselae hirsute, hairs tawny to reddish, 0.5–1 mm; pappi often of both scales and bristles) Peucephyllum
56 Phyllaries 40–60+ in 3–5 series (often in vertical ranks) Chrysothamnus
56 Phyllaries 7–25 in 3 series > 57
57 Involures campanulate, globose, or hemispheric, 4–13 × 7–16 mm; florets 13–45 Acamptopappus
57 Involures turbino-cylindric, 4–5.5 × 2–3 mm; florets 3–7 (functionally staminate) Amphipappus
58 Shrubs (stems ± tomentose; leaf blades obscurely pinnate; heads borne singly or in loose, corymbiform arrays; pappi of 1 or 3–5 scales) Pentzia
58 Annuals, biennials, perennials, or subshrubs > 59
59 Leaves usually 1–3-pinnate (usually aromatic when crushed); phyllary margins usually notably scarious; style-branch appendages essentially none; pappus scales usually rudimentary (3–5, subulate in Sphaeromeria) > 60
59 Leaves usually not lobed, sometimes 1–4-pinnate (seldom notably aromatic when crushed); phyllary margins seldom notably scarious; style-branch appendages mostly deltate to lanceolate or linear; pappus scales usually conspicuous (sometimes associated with bristles) > 62
60 Annuals; heads discoid Matricaria
60 Perennials; heads disciform (peripheral florets pistillate) > 61
61 Heads usually in lax to dense, corymbiform arrays, rarely borne singly; involucres (3–)5–10 mm diam.; florets 60–300+ Tanacetum
61 Heads usually (8–20+) in tight, capitate arrays; involucres (2–)3–4 mm diam.; florets 30–50+ Sphaeromeria
62 Phyllaries 25–125 in 3–9 series; pappi of scales only or of 5–20 scales plus 20–100+ bristles > 63
62 Phyllaries 6–25(–60) in 2–3 series; pappi mostly wholly of scales (usually 5, 10, 15, or 20, subulate-aristate scales in Pentachaeta) > 65
63 Phyllary apices often looped, hooked, patent, recurved, straight, or incurved; pappi fragile or readily falling, of 8–15 subulate to setiform scales Grindelia
63 Phyllary apices usually erect and straight, sometimes spreading or reflexed; pappi persistent or readily falling, usually of scales plus bristles > 64
64 Heads usually in corymbiform, ± paniculiform, or subumbelliform arrays, sometimes borne singly; phyllaries in 3–5 series, unequal, usually thickened or keeled, 1-nerved (nerves not golden-resinous); cypselae 3-angled or 4–12-ribbed Heterotheca
64 Heads borne singly or in 2s or 3s; phyllaries in 2–3 series, equal or subequal, flat, usually 1–3-nerved (nerves golden-resinous); cypselae 2-nerved Erigeron
65 Cypselae narrowly clavate to oblanceoloid, or columnar to obconic or obpyramidal (lengths usually 3+ times diams., if stouter, usually ± compressed) > 66
65 Cypselae stoutly obconic to obpyramidal (lengths usually 1–2, rarely to 3.5, times diams.) > 68
66 Leaves usually sessile, sometimes obscurely petiolate (rarely truly petiolate); pappus scales often aristate, not medially thickened Pentachaeta
66 Leaves usually petiolate (± sessile in some spp. of Chaenactis); pappus scales sometimes aristate or lacerate, often notably medially thickened > 67
67 Pappus scales 4–20, not lacerate (usually erose, sometimes uniaristate) Chaenactis
67 Pappus scales 5, lacerate (divisions bristlelike) Trichoptilium
68 Phyllaries usually strongly reflexed in fruit; receptacles mostly globose (sometimes with setiform enations); disc corollas often brown-purple to red-brown or tipped with brown-purple to red-brown (tubes much shorter than abruptly much-dilated, urceolate to campanulate throats, lobes often shaggily hairy, hairs ± moniliform) > 69
68 Phyllaries mostly erect to spreading in fruit; receptacles flat, conic, domed, hemispheric, or ovoid (smooth or pitted, without setiform enations); disc corollas usually uniformly yellow to cream, sometimes purplish to reddish (tubes much shorter than to about equaling slightly dilated, funnelform to cylindric throats, lobes not shaggily hairy with moniliform hairs) > 70
69 Stems not winged (receptacles usually with setiform enations; style-branch apices ± attenuate) Gaillardia
69 Stems often winged (by decurrent leaf bases; receptacles rarely with setiform enations; style-branch apices penicillate or truncate) Helenium
70 Leaf blades simple or 1–2-pinnately lobed (lobes mostly filiform, linear, or oblong), ultimate margins entire or toothed, faces glabrous or hairy, usually ± gland-dotted (often in pits); phyllaries persistent (or inner falling), usually (6–)6–30(–40) in 2 series and unequal (outer usually connate), sometimes 28–50 in 2–3 series and subequal (usually spreading to erect in fruit) Hymenoxys
70 Leaf blades mostly oblanceolate to linear or filiform, sometimes lobed, ultimate margins usually entire, sometimes toothed, faces glabrous or ± hairy, eglandular or ± gland-dotted; phyllaries usually persistent, 11–60+ in 2–3 series (mostly spreading to erect in fruit, distinct, herbaceous; outer with or without scarious margins, abaxial faces ± hairy; mid usually same number as, alternating with, and similar to outer, almost always with ± scarious margins; inner narrower than others, margins scarious) Tetraneuris
Facts about "Asteraceae"
AuthorTheodore M. Barkley† +, Luc Brouillet + and John L. Strother +
Common nameComposite Family +
Referenceantonio2001a +, bayer1998b +, bentham1873a +, bremer1987a +, bremer1994a +, bremer1996a +, carlquist1966a +, carlquist1976a +, cronquist1955a +, cronquist1955b +, cronquist1977a +, cronquist1980a +, cronquist1994a +, eldenas1999a +, heywood1977a +, hind1995a +, hind1996a +, jansen1991a +, jansen1992a +, jeffrey1978a +, jeffrey1995a +, kim1992a +, kim1995a +, king1975a +, mabry1990a +, panero2002a +, robinson1996a +, small1919a +, stuessy1996a +, turner1996a + and wagenitz1976a +
SynonymCompositae +
Taxon nameAsteraceae +
Taxon rankfamily +
VolumeVolume 19 +