Polygalaceae

Hoffmannsegg & Link
Common names: Milkwort Family
Treatment appears in FNA Volume 10.

Herbs, annual, biennial, or perennial, subshrubs, shrubs, [trees, or lianas], synoecious, terres­trial, usually unarmed (sometimes thorns present as modified tips of racemes in Rhinotropis), sometimes clonal. Rootstock usually brownish to whitish, usually not exfoliating. Stems mostly erect, sometimes laxly so, or decumbent, prostrate, or creeping. Leaves usually alternate, some­times opposite or whorled, simple, basal and/or cauline, basal usually not present at anthesis; stipules absent [present as glands]; petiolate or not; blade mostly ± uniform in shape and size, sometimes weakly to strongly dimorphic, pinnately veined, secondary venation usually obscure, usually not punctate, margins entire (rarely erose or appearing minutely serrulate). Inflores­cences terminal, axillary, or leaf-opposed, usually racemes, sometimes panicles, spikes, corymbs, fascicles, or reduced to 1–5 flowers; bract 1; bracteoles present. Flowers bisexual, sometimes cleistogamous and subterranean or in proximal leaf axils, bilaterally [radially] symmetric, usually pedicellate, rarely sessile, pedicel usually not winged; perianth and androecium hypogy­nous [perigynous]; sepals persistent or deciduous, 5, imbricate in bud, unequal with 3 outer sepals, 1 upper and 2 lower (these 2 sometimes connate and appearing as 1 or 2-lobed), 2 lateral inner sepals (wings) expanded and petaloid [± similar to outer sepals], adnate proximally to petals and filaments; petals 3(or 5), upper 2 often apically reflexed at anthesis, lower 1 (keel) conduplicate and, sometimes, apically lobed and/or crested (crest typically fimbriate), rarely with 2 reduced lateral petals; stamens [2–](6 or 7)8(or 9)[10]; filaments connate [distinct]; anthers basifixed, dehiscent by 1 or 2 apical or subapical pores to very short slits [to introrsely longitudinally dehiscent]; pistil 2[–8]-carpellate, syncarpous; ovary superior, (1 or)2[–8]-locular; placentation axile; style 1; stigmas 2; ovule 1 per locule [2–40]. Fruits capsules or pseudomonomerous and samaroid [samaras, drupes, or berries], somewhat isodiametric to slightly oblong, pubescent or glabrous. Seeds 1 per locule, ± blackish at maturity in capsular species, ellipsoid, smooth (pitted in some Polygala), often whitish pubescent, usually arillate (the aril-like structure from integuments, not funiculus, thus called an arillode by some, a caruncle by others).

Distribution

North America, Mexico, West Indies, Central America, South America, Europe, Asia, Africa, Australia.

Discussion

Genera 29, species ca. 1200 (6 genera, 53 species in the flora).

B. Eriksen and C. Persson (2007) provided a good synthesis of the taxonomic history of Polygalaceae, with modern phylogenetic hypotheses presented by Persson (2001), F. Forest et al. (2007), and J. R. Abbott (2009). All but one of the North American species have traditionally been treated within a broadly defined Polygala. At least six major clades within Polygala (in the traditional broad sense) are represented natively in North America (Abbott). These clades correspond to morphological differences and traditional infrageneric groups, in many cases correlated with geographic distribution. A seventh clade, represented by the type group and based on P. vulgaris, is native to Eurasia and is represented by one sparsely naturalized species. Multiple lines of robust evidence support that four of these native clades are so distant phylogenetically from the type group of Polygala that they can no longer be maintained within Polygala: the groups here recognized as the genera Asemeia, Hebecarpa, Polygaloides, and Rhinotropis, all of which correspond to traditional subgenera.

Much cytological and karyological variation has been documented in the small percentage of Polygalaceae that have been studied cytologically. Some species, including a few North American taxa, have different chromosome numbers, with discrepancies and uncertainties as to the base number for many groups. Even if some reports are in error, evidence of polyploid and aneuploid series is clear, as well as widespread hybridization in a few species, although few reports of hybridization are documented (T. L. Wendt 1978; A. J. Lack 1995). The taxa represented here generally do not intergrade.

The diversity of reported chromosome numbers for North American taxa shows several ploidy shifts, even within some taxa. The exact patterns cannot be fully tracked, given the number of taxa with undocumented chromosome numbers and the absence of solid hypotheses of sister taxa relationships. Despite the shortcomings of current cytological data, further investigations should be useful for illuminating relationships among North American Polygalaceae. There may still be diagnostic value, and even phylogenetic information, in the cytological and karyological data (T. L. Wendt 1978; J. A. R. Paiva 1998).

B. Eriksen and C. Persson (2007) noted Polygalaceae have little economic importance except in herbal medicine (for example, A. Freire-Fierro 1995). The North American Polygala senega is perhaps the most economically important taxon, with some commercial usage globally for various medicinal purposes (J. M. Gillett 1968b; C. J. Briggs 1988). Many species of Polygalaceae are showy in flower and are sometimes cultivated as ornamentals. Most commonly encountered in North America are P. myrtifolia, P. virgata Thunberg, P. ×\dalmasiana L. H. Bailey (perhaps a form of P. myrtifolia), and Polygaloides chamaebuxus (Linnaeus) O. Schwarz.

Use of the term subshrub refers to a low, multi-stemmed, suffrutescent perennial herb; the herbaceous branches may be erect or decumbent, but they are woody above ground proximally. The term subsessile refers leaves with a petiole to 0.5 mm. Measurements of raceme length refer to the flowering and/or fruiting portion (including attachment scars), while width refers to the broadest portion with open (or nearly so) flowers. Raceme shape refers to the flowering and fruiting portion only; with age, there is often an elongated basal portion with scars left by the deciduous fruits. In descriptions of flower color, the outer sepals are not included, and it should be understood that the wings and petals are almost always paler in the proximal portion. The outer sepals are usually green, unless otherwise stated, although it is relatively common for some sepals to be whitish, pinkish, or purplish red marginally. It is also very common for the tips of the upper petals to be darker and for the apex of the keel to be greenish or yellowish. On drying, colors can become darker or paler, with whites often taking on a bluish or pinkish purple tinge, but, unless otherwise stated, the colors do not change dramatically. In key leads and descriptions for Polygalaceae, lower sepals refers to abaxial sepals and upper sepals refers to adaxial sepals; the two lateral (inner, often petaloid) sepals are referred to as wings. In reference to petals, the abaxial (lower) petal is referred to as the keel. Unless otherwise stated, if the sepals are deciduous, so are the wings and corolla; conversely, if the sepals are persistent (unless only the upper one is specified), then so are the wings and corolla. Descriptions of pubescence do not refer to marginal cilia; even a glabrous structure may be marginally ciliate. Measurements of seed length include aril and pubescence; the body itself is usually 0.3–0.7 mm shorter.

Selected References

None.

Key

1 Ovaries 1-loculed; fruits indehiscent; keel petals entire, ± 3-lobed; seeds glabrous, not arillate; annuals. Monnina
1 Ovaries 2-loculed (sometimes 1 abortive); fruits dehiscent; keel petals with crest or beak or entire; seeds usually pubescent, usually arillate; annuals, biennials, perennials, subshrubs, or shrubs. > 2
2 Keel petals with lobed crests, often fimbriate. > 3
3 Flowers and wing sepals 1–9(–10) mm; stems mostly erect (not creeping, rarely laxly decumbent or prostrate in a few species); leaves usually numerous, distributed evenly along stem or clustered in basal rosettes; all sepals usually persistent. Polygala
3 Flowers 15+ mm, wing sepals (10–)13–20 mm; stems creeping or decumbent with short, erect shoots; leaves few, well-developed ones ± clustered distally; all sepals deciduous. Polygaloides
2 Keel petals entire and blunt or beaked (with unlobed projection), without lobed crest. > 4
4 Lower 2 sepals connate 3/4 their length; all sepals persistent. Asemeia
4 All sepals distinct (or appearing very slightly connate basally); all sepals usually deciduous, occasionally upper sepal persistent or rarely all sepals persistent. > 5
5 Shrubs or subshrubs; raceme rachis thorn-tipped. Rhinotropis (in part)
5 Perennials, shrubs, or subshrubs; raceme rachis not thorn-tipped. > 6
6 Keel petals not beaked, sometimes bluntly 3-lobed; all sepals deciduous (sometimes upper 1 tardily so or subpersistent in H. macradenia and H. punctata). Hebecarpa
6 Keel petals beaked, with unlobed projection, this sometimes reduced or obscure (rarely on all flowers of a given plant unless all flowers are cleistogamous); upper sepals persistent, others deciduous (except all sepals deciduous in R. californica and R. cornuta, and all sepals persistent in R. rusbyi). Rhinotropis (in part)
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