Knot Grass

Panicum firmulum Hitchc. & Chase, Contr. U. S. Nat. Herb. 15:
27. 1910.
Plants light olive-green, rather loosely tufted, ascending or decumbent at base, from creeping knotted rootstocks as much as 5 cm. long; culms 30-40 cm. high, simple or with a few appressed branches, glabrous, the nodes glabrous or strigose; leaf-sheaths overlapping, striate, papillose-pubescent, papillose only, or nearly glabrous, a tuft of stiff hairs 3 mm. long on the sides at the summit; ligule dense, about 1.5 mm. long; blades ascending or spreading, firm, 4r-10 cm. long, the lower shorter and more spreading, 4-7 mm. wide, abruptly acuminate, rounded at the base and wider than the sheath, sparsely papillose-ciliate, at least toward the base, scabrous on the upper surface; panicles slender, interrupted, their branches erect, the branchlets bearing 1-3 short-pediceled spikelets, the setiform prolongation of the axis usually about as long as the spikelets, sometimes twice as long; spikelets 3-3.2 mm. long, 1.7-1.8 mm. wide, obovate, subacute, turgid, strongly nerved; first glume clasping, half the length of the spikelet, pointed, 5-7-nerved; second glume and sterile lemma subequal, scarcely covering the fruit, 5-7-nerved, the glume obscurely reticulate toward the summit; fruit 2.7-2.8 mm. long, 1.6-1.7 mm. wide, ob ovate-elliptic, abruptly acute, very turgid.
Type locality: Elsordo, Zapata County, Texas. Distribution: Southern Texas.