GRAMINE^J. (GRASS FAMILY.) 415 



4. D. latifolia, Hook. Stem 1 to 2 feet high : lower haves 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 silky hairs ^ as long or more; aivn stout, attached fust above the 

 middle, somewhat divergent, Exceeding the flowering glume hnt included by 

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

 and westward into Oregon and Washington Territory. 



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 Sf Harbour), 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, Bolaud. 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 own 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, from dense tufts 

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

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

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

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



