Annuals, 5–120 cm (mostly self-incompatible). Stems erect to spreading (unbranched or branched). Leaves basal and cauline (at least basal mostly withering before flowering); usually mostly alternate (opposite in C. oppositifolia); sessile; blades linear (grasslike), margins entire or sparsely toothed (revolute), faces often scabrous. Heads radiate, usually borne singly or in open to dense, corymbiform or ± spiciform arrays, sometimes in axillary glomerules. Peduncular bracts (and reduced, distal leaves; peduncles often relatively short, bracts crowded, closely subtending phyllaries): tack-glands 0 or 1–6+ (at tips and, sometimes, on margins; margins sometimes thickened or rolled, often proximally pectinate and/or ciliate). Phyllaries falling or persistent, 1–6 in 1 series (each partly enveloping a ray cypsela, commonly with simple and/or tack-glands). Receptacles ± flat, hairy, paleate (paleae falling or persistent, in 1 series between rays and discs, ± connate, forming plicate cups, distinct apices usually acute to acuminate). Ray florets 1–6, pistillate, fertile; corollas white or cream to rose, or yellow, sometimes with proximal dark-red spot (laminae 3-lobed, lobes spreading or ± parallel, lengths 1/4+ total laminae). Disc florets 1–25, usually bisexual and fertile; corollas white or cream to rose, or yellow, tubes shorter than throats, lobes 5, deltate to lance-ovate (anthers usually dark purple, rarely yellow or light brown). Ray cypselae usually obcompressed (± 3-angled, abaxial sides ± 2-faced, angles between those faces 90+°, adaxial sides ± flat, overall smooth or rough-wrinkled, glabrous or hairy); pappi 0. Disc cypselae narrowly clavate (usually angled in cross section, glabrous or hairy); pappi usually of 6–13 subulate to lanceolate-aristate or shorter and broader scales (longer and shorter often alternating), rarely 0. x = 4, 5, 6, 7.
w United States.
Species 10 (10 in the flora).
Calycadenia is nearly confined to the Central Valley and adjacent lower elevations of bordering mountain ranges of California. R. L. Carr and G. D. Carr (1993) recognized nine species; a tenth species is included here. All species except C. hooveri and C. micrantha are strongly self-incompatible. The genus appears to exhibit two contrasting modes of evolution (G. D. Carr 1977). One group of taxa (C. pauciflora and C. fremontii complex) comprises distinct chromosome races that lack clear and consistent morphologic differentiation. The chromosome races are differentiated primarily by reciprocal chromosome translocations and, in some cases, paracentric inversions (G. D. Carr 1975, 1975b, 1977, 1980; Carr and Carr 1983, 2000). In contrast, C. multiglandulosa and C. hispida (combined in this treatment) consist of distinct morphologic races (D. D. Keck 1960b) and lack chromosomal differentiation. Our incomplete understanding of the biology of this genus makes the production of a clear, concise, and practical taxonomic treatment difficult.
Baldwin, B. G. and S. Markos. 1998. Phylogenetic utility of the external transcribed spacer (ETS) of 18S-26S rDNA: Congruence of ETS and ITS trees of Calycadenia (Compositae). Molec. Phylogen. Evol. 10: 449–463.
|1||Peduncular bracts (and, sometimes, paleae): tack-glands (0–)2–6+ (some Butte County plants of C. fremontii and C. pauciflora with fewer tack-glands are usually less than 20 cm); ray laminae: central lobes equaling or narrower than laterals, widest near or beyond middles (except in C. multiglandulosa, with copious tack-glands on peduncular bracts and paleae)||> 2|
|1||Peduncular bracts: tack-glands (0–)1 (and terminal), or 3–6+ (and confined to thickened or rolled margins in Calycadenia mollis); paleae: tack-glands 0; ray laminae: central lobes usually notably smaller than laterals, widest at bases (widest beyond middles in Calycadenia mollis)||> 5|
|2||Leaves opposite (heads in congested, axillary and terminal glomerules, appearing whorled)||Calycadenia oppositifolia|
|2||Leaves mostly alternate (sometimes opposite to beyond midstems in C. multiglandulosa; heads borne singly or in glomerules in corymbiform or spiciform arrays, not appearing whorled)||> 3|
|3||Ray laminae: central lobes widest at bases (notably smaller and narrower thanlaterals)||Calycadenia multiglandulosa|
|3||Ray laminae: central lobes widest near or beyond middles (± similar to laterals)||> 4|
|4||Stems branched (plants usually without obvious axes, branches relatively many, slender, usually divergent, often zigzag); paleae 4–6 mm (receptacular cups± clavate to fusiform, lengths ± 2 times diams.); ray florets 1(–2), corollas whiteto reddish; disc florets 2–5||Calycadenia pauciflora|
|4||Stems simple or branched (plants with main axes usually obvious, except in some populations centered in Butte, s Lake, and Sonoma counties, branches relatively few, ± rigid); paleae 3–7 mm (receptacular cups ± campanulate, lengths ± equaling diams.); ray florets (1–)2–6, corollas white or cream to pinkish, or yellow (laminae sometimes basally reddish); disc florets (4–)6–21||Calycadenia fremontii|
|5||Peduncular bracts: apices rounded, tack-glands mostly 3–6+ (confined to thickened or rolled margins); ray laminae: central lobes slightly narrower than laterals, widest beyondmiddles||Calycadenia mollis|
|5||Peduncular bracts: apices concave, rounded, or truncate, tack-glands usually 1 (terminal); ray laminae: central lobes notably smaller than laterals, widest at bases||> 6|
|6||Corollas yellow; ray cypselae rough-wrinkled||> 7|
|6||Corollas white (sometimes fading reddish); ray cypselae usually smooth (rough-wrinkled in some C. hooveri)||> 8|
|7||Plants 20–120 cm (sometimes robust); ray laminae (4–)5–12 mm||Calycadenia truncata|
|7||Plants 10–50 cm (relatively slender); ray laminae 2–2.5(–3) mm||Calycadenia micrantha|
|8||Stems branched (branches flexible); ray florets (0–)1(–2); disc florets 1–2; ray cypselaeglabrous||Calycadenia hooveri|
|8||Stems branched (branches rigid); ray florets 1–5; disc florets 4–15; ray cypselae densely appressed-hairy||> 9|
|9||Peduncular bracts lance-elliptic (flat distally), apices rounded to truncate||Calycadenia villosa|
|9||Peduncular bracts narrowly lanceolate or lance-attenuate (± cylindric distally 1–3+ mm), apices truncate to strongly concave||Calycadenia spicata|