Compilation
Setaria humifusa

Annual, loosely tufted, 1 to over 2 ft. high, or sometimes stunted and only a few inches high. Culms slender, glabrous, or sometimes somewhat stout downwards, smooth or slightly rough below the inflorescence, geniculately ascending, rarely erect from the base, weak, 2–4- rarely more-noded, simple or sparingly branched from below, the uppermost internode (peduncle) at length as long as or much longer than the remainder of the culm, long-exserted, the lower internodes usually more or less compressed. Leaf-sheaths thin, upwards herbaceous, the lower compressed and upwards finely keeled, the upper terete, all glabrous and smooth; ligule reduced to a ciliate rim; blade linear from a slightly or obscurely contracted base, long-tapering to a slender point, from a few inches to 1 ft. long by 2–4 lin. wide, flat, weak to flaccid, green, often slightly glaucous, quite glabrous or with some long white hairs towards the base, slightly rough along the margins upwards, midrib and primary lateral nerves (about 3 on each side) very fine. Inflorescence an erect dense continuous oblong-or linear-cylindric false spike, up to 4 in. long by 3–4 lin. wide (exclusive of the bristles), fulvous to rufo-fulvous; rhachis slender, terete, subangular, minutely tomentellous; branches reduced to a sessile involucre each supporting a solitary perfect spikelet frequently with a more or less arrested companion; bristles 6–8 to each involucre, slender, rigid, scaberulous, very unequal, up to 3–4 lin. long, pale at the base, fulvous to rufous upwards; pedicels reduced to small stumps with discoid tips. Spikelets broadly oblong to elliptic in back view, semi-ovate-elliptic in profile, 1 1/2 lin. long by 3/4 lin. wide, pale green in flower, rather turgid when mature. Glumes membranous, tightly appressed, rotundate-ovate, subacute to obtuse; lower one-third to two-fifths the length of the spikelet, 3-nerved; upper from less than half to two-thirds the length of the spikelet, 5-nerved. Lower floret ♂ or in particularly weak specimens barren, as long as the upper: valve membranous, 5-nerved, very flat or somewhat depressed on the back; valvule as long as the valve or somewhat shorter, broadly elliptic, acute, keels marginate; perfect anthers up to 3/4 lin. long. Upper floret broadly boat-shaped, very convex on the back: valve crustaceous, distinctly transversely rugose, yellowish to almost orange in colour, rarely fuscous when mature; valvule granular-punctate, with stout keels; anthers 3/8 lin. long. Grain rotundate-elliptic in back view, plano-convex; hilum punctate; scutellum ovate, more than half the length of the grain.