87. Polymnia L. (leaf cup)

Plants perennial herbs (annuals elsewhere), usually colonial from rhizomes. Stems erect or ascending, usually several-branched, with fine longitudinal lines or ridges, occasionally bluntly angled, the internodes of the main stems often hollow, glabrous or moderately to densely pubescent with nonglandular or gland-tipped hairs toward the tip. Leaves opposite or the uppermost few alternate, sessile or short-petiolate, the bases mostly slightly or greatly expanded and wrapping around the stem. Leaf blades ovate to broadly oblong-ovate or broadly elliptic, more or less pinnately 3–11-lobed, tapered or more or less truncate at the base, relatively thin in texture, the main lobes tapered to a sharply pointed tip, the margins finely to coarsely toothed and hairy, the surfaces glabrous or sparsely to moderately pubescent with short, soft, curved hairs, the undersurface pale green and usually with minute, sessile, spherical, yellow glands. Inflorescences of relatively open, irregular, often spreading to nodding clusters at the branch tips, these sometimes appearing as small panicles, subtended by leaflike bracts at the branch points, the heads mostly with relatively short, glabrous or more commonly hairy and/or glandular stalks. Heads radiate but sometimes appearing discoid. Involucre cup-shaped, the bracts in 2 dissimilar series, those of the outer series usually narrower and slightly shorter or longer than the others. Involucral bracts loosely ascending, those of the inner series slightly longer than the chaffy, outermost bracts, oblong-lanceolate to elliptic or broadly ovate, mostly narrowed or tapered to a sharp point at the tip, the margins with minute or spreading hairs, the outer surface glabrous or sparsely to densely pubescent with gland-tipped hairs, the outer series of bracts green and somewhat leaflike, at least toward the tip. Receptacle flat or shallowly convex, not elongating as the fruits mature, with chaffy bracts subtending the ray and disc florets, narrowly ovate to obovate, thin and papery, concave and wrapped around the florets. Ray florets 4–7 (2 or 3 elsewhere), pistillate (with a 2-branched style exserted from the short tube at flowering), the corolla sometimes with a short or absent ligule (then reduced to a minute tube), when present the ligule relatively broad, white or pale cream-colored, the short, tubular base moderately to densely short-hairy and/or glandular, withered and often not persistent at fruiting. Disc florets 12–40, staminate (with a small, stalklike ovary and a more or less undivided style), the corolla light yellow to pale yellow, often sparsely glandular toward the tip, not expanded at the base. Style branches with the sterile tip somewhat elongate and tapered. Pappus of the ray and disc florets absent. Fruits 3–4 mm long, elliptic-obovate to slightly pear-shaped in outline, slightly flattened, with 3–6 blunt angles or less commonly ribs, the surface otherwise glabrous, dark brown to black, sometimes with lighter brown mottling, somewhat shiny. Three species, eastern U.S., Canada.

Most authors (Steyermark, 1963; Wells, 1965; Barkley, 1986; Gleason and Cronquist, 1991) have included the species of Smallanthus in Polymnia, but Robinson (1978) noted differences in morphology and anatomy of the achenes, pubescence patterns of the florets, and chromosomal base number that appear to justify separating the two genera. The third species of Polymnia in the restricted sense is P. cossatotensis Pittman & V.M. Bates, which is endemic to the Ouachita Mountain region of west-central Arkansas. This taxon is distinguished readily from the rest of the genus by its annual habit, mostly unlobed leaves that are cordate at the base, and relatively small heads with only 2 or 3 pistillate florets.