15. P. scopàrium, Lam. Culms upright, at length much branched and reclining (1–2° long), roughish; leaves lanceolate (3–5´ long by {1/3}–½´ wide), rather faintly 9-nerved, hairy or smooth, fringed on the whole margin or next the base with long and stiff spreading hairs, the sheaths bristly throughout with similar hairs; panicle open, nearly simple, bearing few tumid-obovate hairy or smoothish spikelets about 1½´´ long; lower glume roundish, about half or a quarter of the length of the upper one. (P. pauciflorum, Ell.)—Wet meadows and copses, E. Mass. to Minn., west and southward. June, July.
16. P. commutàtum, Schultes. Rather slender, erect, 1–2° high, nearly glabrous; leaves lanceolate, acuminate (3–6´ long), the margins toward the base and the sheaths sparsely ciliate; panicle spreading, often short-peduncled; spikelets scattered, glabrous, oblong, acutish, little more than 1´´ long; lower glume ovate, often acute.—N. Y. to Fla.—A frequent variety with smaller spikelets (not 1´´ long) approaches the next, and has also been confused with P. dichotomum.—Ont. to Va. and southward.
[=][=] Spikelets less than 1´´ long.
17. P. nítidum, Michx. (Lam.?) Resembles the last; leaves rather thick and the principal nerves very obscure or none except at the base; panicle broad, more slender; spikelets smaller ({2/3}´´ long), broadly ovate and very obtuse; lower glume very obtuse. (P. sphærocarpon, Ell.)—N. Y. to Ga., and westward.
18. P. microcárpon, Muhl. Like the last; the broadly lanceolate leaves nearly similar, but usually longer (8´ long or less), distinctly nerved; panicle soon exserted on a slender peduncle, rather narrower, with numerous slender branches and very many-flowered (3–7´ long); spikelets about ½´´ long, ovoid, smooth or smoothish; lower glume orbicular and very small.—Dry or moist thickets, Penn. to Mich., Neb., and southward. July–Sept.
[++][++] Culm-leaves linear or sometimes narrowly lanceolate (basal often lanceolate); primary nerves often indistinct or none; spikelets small.
19. P. depauperàtum, Muhl. Culms simple or branched from the base, forming close tufts (6–12´ high), terminated by a simple and few-flowered contracted panicle, often much overtopped by the narrowly linear and elongated (4–7´) upper leaves; spikelets ¾–1½´´ long, oval-obovate, commonly pointed when young; lower glume ovate.—Varies, with the leaves involute, at least when dry (P. involutum, Torr.), and with the sheaths either beset with long hairs or nearly smooth; the panicle either partly included, or on a long and slender peduncle.—Dry woods and hills; rather common. June.
20. P. consanguíneum, Kunth. Culms slender, 1–2° high, often decumbent and rooting below; nearly glabrous or the sheaths and leaves somewhat pubescent or villous; panicle small, with rather few spreading few-flowered branches; spikelets 1–1½´´ long, oblong-obovate, acutish.—Dry woods, Norfolk, Va., and south to Fl. and Tex.
21. P. dichótomum, L.! Culms (8´–2° high) at first mostly simple, bearing a more or less exserted spreading compound panicle (1–3´ long), and linear to linear-lanceolate flat leaves (those tufted at the root usually ovate-lanceolate and very short, thickish); but commonly branching later in the season, the branches often clustered, and bearing nearly simple and included small panicles; spikelets ½-{2/3}´´ long, elliptical, obtuse, downy or smooth; lower glume roundish.—Common everywhere. Very variable both in habit and in the amount of villosity (depending upon the soil, exposure, season, etc.), so that it is difficult to specify any well defined varieties. The more conspicuous forms are (a) commùne, with simple culms erect or ascending, and leaves suberect, usually pale green—(b) fasciculàtum, with clustered leafy branches and short peduncles, a common autumnal state—and (c) grácile, the culms lax, very slender and elongated, with rather distant spreading leaves (usually bright green), and mostly long-pedunculate panicles.
22. P. laxiflòrum, Lam.! Closely resembling the last species, in its several forms; distinguished by the larger acutish spikelets (nearly or quite 1´´ long).—Common.