MANUAL OF THE GRASSES OF THE UNITED STATES 



6- to 8-flowered, about 1 cm. long, 

 pale to purplish, nearly terete; glumes 

 scaberulous, about as long as the 

 lower florets; lemmas about 5 mm. 

 long, densely pilose on the lower half 

 of the nerves and on the callus, ob- 

 tuse, entire or minutely notched, the 

 midnerve not exserted; palea half or 

 two-thirds as long as the lemma, 

 densely pilose on the keels and puber- 

 ulent on the back. % — Plains and 

 rocky slopes, Texas to southeastern 

 California, north to Nevada and 

 Utah; Mexico. 



217 



Figure 290. — Tridens mu- 

 ticus. Panicle, X 1 ; two 

 views of floret, X 5. 

 (Chase 5902, Tex.) 



17. Tridens elongatus (Buckl.) 

 Nash. Rough tridens. (Fig. 291.) 

 Culms erect, tufted, 40 to 80 cm. tall ; 



Figure 291. — Tridens elonga- 

 tus. Panicle, X 1; two views 

 of floret, X 5. (Ball 1535, 

 Tex.) 



sheaths and bjades scaberulous, some- 

 times sparsely pilose, the blades 

 mostly flat, 2 to 4 mm. wide, tapering 

 to a fine point ; panicle elongate; erect, 

 pale or purple-tinged, loosely flow- 

 ered, 10 to 25 cm. long, the branches 

 rather distant, appressed, scarcely or 

 not at all overlapping; spikelets sim- 

 ilar to those of T. muticus, the glumes 

 longer, the hairs on the florets not so 

 long. % (Tricuspis elongata N ash.) 

 — Plains, sandy prairies, and rocky 

 slopes, Missouri to Colorado, Texas, 

 and Arizona. 



34. TRIPLASIS Beauv. 



Spikelets few-flowered, V-shaped, the florets remote, the rachilla slender, 

 disarticulating above the glumes and between the florets; glumes nearly 

 equal, smooth, 1-nerved, acute; lemmas narrow, 3-nerved, 2-lobed, the nerves 

 parallel, silky-villous, the lateral pair near the margin, the midnerve excurrent 

 as an awn, as long as the lobes or longer; palea shorter than the lemma, the 

 keels densely long-villous on the upper half. Slender tufted annuals or peren- 

 nials, with short blades, short, open, few-flowered, purple, terminal panicles and 

 cleistogamous narrow panicles in the axils of the leaves. Both species have, in 

 addition to the small panicles of cleistogamous spikelets in the upper sheaths, 

 additional cleistogamous spikelets, usually reduced to a single large floret, at 

 the bases of the lower sheaths. The culms break at the nodes, the mature 



