GRAMINE^E. (GRASS FAMILY.) 415 



4. D. latifolia, Hook. Stem 1 to 2 feet high : lower leaves 2 or 3 inches 

 long, about 3 lines wide, flat and smooth : panicle with a few slender rays, 

 which are densely flowered above : outer glumes ovate-lanceolate : flowering 

 glume with silk// hairs £ as long or more ; awn stout, attached just above the 

 middle, somewhat divergent, exceeding the flowering glume but included by 

 the outer ones. — Aira latifolia, Hook. In the Northern Rocky Mountains, 

 and westward into Oregon and Washington. 



24. TRISETUM, Pers. 



Perennials, resembling the next genus and by some made a section under 

 it. Ours have a dense and spike-like panicle, and a smooth ovary. 



1. T. SUbspicatum, Beauv. Stems tufted, 4 inches to 2 feet high, 

 smooth or downy : leaves flat and smooth, or with the loose sheaths pubes- 

 cent : panicle 2 to 6 inches long, dense and oblong-ovate, or elongated and 

 several times interrupted below : lower glume shorter, the upper about equal- 

 ling the florets, both ciliate on the keel : flowering glume with a divergent 

 awn about its own length. — In the mountains from Colorado to California 

 and northward ; eastward along the northern border to New England. 



Var. molle, Gray. Stem and foliage minutely soft-downy. — Man. 641. 

 Same range. 



25. A VENA, L. Oat. 



The grain is oblong-linear, grooved on one side, hairy throughout or at the 

 tip only, free but closely invested by the palet. 



1. A. Striata, Michx. Glabrous and smooth throughout, slender, 1 to 

 2 feet high : leaves narrow : panicle simple, loose, with spikelets on capillary 

 pedicels: lower glume 1 -nerved; the upper 3-nerved : flowers short-bearded 

 at base ; the soon bent or divergent awn inserted just below the tapering very 

 sharply cuspidate 2-cleft tip of the palet. — Colorado (Hall fy Harbour) t and 

 in the mountains of New York and New England. 



26. DA NTH ONI A, DC. Wild Oat Grass. 



Ours are perennials, with narrow leaves, hairy sheaths, and a small simple 

 panicle or raceme. 



1. D. Calif ornica, Boland. Stems sometimes decumbent at base, 

 from ^ to 3 feet high : leaves, especially the lower, convolute and setaceously 

 pointed, with sheaths bearded at the throat: panicle mostly a simple raceme: 

 outer glumes mostly purplish with scarious margins, pointed, the upper 5 to 

 7-nerved : flowering glume broad, its teeth about half its oivn length, with mar- 

 ginal tufts of long silky hairs at or below the middle ; awn about equalling the 

 glume. — Proc. Calif. Acad. ii. 182. 



Var. unispicata, Thurber. Stems 6 inches high or less, /5w?i dense tufls 

 of somewhat hairy leaves, the sheaths of which are densely villous with white spread- 

 ing hairs, arising in small clusters from white minute papilla; : spikelet solitary 

 and terminal (rarely 2 or 3). — Bot. Calif ii. 294. Both forms occur in the 

 Rocky Mountains, the Wasatch, and westward to California and Oregon. 



