Annual or perennial grasses with flat or convolute leaf-blades and numerous spikelets in one-sided spikes. Spikelets 1-2-flowered, arranged in two rows on one side of a flat rachis, the rachilla extended beyond the base of the flowers, bearing 1-3 awns and 1-3 rudimentary scales. Two lower scales empty, acute, keeled; flowering scale broader, 3-toothed, the teeth awn-pointed or awned; palet hyaline, entire or 2-toothed. Stamens 3. Styles distinct. Stigmas plumose. Grain oblong, free. [In honor of Claudius Boutelou, a Spanish botanist.]

About 30 species, particularly numerous in Mexico and in the southwestern United States.

1. Bouteloua Hirsuta Lag. Hairy Mesquite-Grass

Fig. 548

B. hirsuta Lag. Var. Cienc. y Litter. 2: Part 4, 141. 1805.

Culms 6'-2o' tall, erect, simple or sometimes sparingly branched at the base, smooth and glabrous. Sheaths mostly at the base of the culm, the lower short and crowded, the upper longer; ligule a ring of short hairs; blades 1'-5' long, 1" wide or less, erect or ascending, flat, scabrous, sparingly papillose-hirsute near the base, especially on the margins; spikes 1-4, Y-2' long, usually erect or ascending, the rachis extending beyond the spikelets into a conspicuous point; spikelets numerous, 2 1/2-3" long, pectinately arranged; first scale hyaline, shorter than the membranous second one, which is strongly papillose-hirsute on the keel; third scale pubescent, 3-cleft to the middle, the nerves terminating in awns; rachilla without a tuft of hairs under the rudimentary scales and awns.

In dry soil, especially on prairies, Illinois to South Dakota and Mexico; also in Florida. Bristly Mesquite, Black Grama; Buffalo-grass. July-Sept.

2. Bouteloua Oligostachya (Nutt.) Torr. Grama-Grass. Mesquite-Grass

Fig. 549

Atheropogon oligostachyus Nutt. Gen. 1: 78. 1818.

B. oligostachya Torr.; A. Gray, Man. Ed. 2, 553. 1856.

Culms 6' -18' tall, erect, simple, smooth and glabrous. Sheaths shorter than the internodes; ligule a ring of short hairs; blades 1'-4' long, 1" wide or less, involute, at least at the long slender tip, smooth or scabrous; spikes 1-3, 1'-2' long, often strongly curved, the rachis terminating in a short inconspicuous point; spikelets numerous, pectinately arranged, about 3" long; first scale hyaline, shorter than the membranous second one, which is scabrous and sometimes long-ciliate on 'the keel, and sometimes bears a few papillae; third scale pubescent, 3-cleft, the nerves terminating in awns; rachilla with a tuft of long hairs under the rudimentary scales and awns.

On prairies, Wisconsin to North Dakota, south to Texas and Mexico. Blue or Common Grama, Buffalo-grass. July-Sept.