282 MISC. PUBLICATION 200, U. S. DEPT. OF AGRICULTURE 



has not been examined, but it was received from Muhlenberg and 

 may be assumed to be the same as the specimen in the Muhlenberg 

 Herbarium described under Aim pallens by Muhlenberg. The only 

 other specimen known is the type of Eatonia aristata 

 collected in South Carolina by Curtiss. 



54. TRISETUM Pers. Trisetum 



Spikelets usually 2-flowered, sometimes 3- to 5-flow- 

 ered, the rachilla prolonged behind the upper floret, 



usually villous; glumes somewhat unequal, acute, the 



second usually longer than the first floret; lemmas 



usually short-bearded at the base, 2-toothed at apex, 



the teeth often awned, bearing from the back below 



the cleft apex a straight and included or usually bent 



and exserted awn (awnless or nearly so in Trisetum 



melicoides and T. wolfii). Tufted perennials (except 



F s G phe*(%>ho 5 ii 5 s l pai- Trisetum interruptum) , with flat blades and open or 



tens, x io. (Cur- usually contracted or spikelike shining panicles. 



Type species, T. flavescens. Name from Latin tri, 



three, and setum, bristle, alluding to the three awns of the lemma. 



Several of the species are valuable for grazing. Trisetum spicatum 



constitutes an important part of the forage on alpine and subalpine 



slopes, and T. wolfii at medium altitudes. 



Spikelets disarticulating below the glumes. 



Plants perennial; panicle lax, somewhat open 9. T. pennsylvanicum. 



Plants annual; panicle narrow, dense, interrupted 10. T. interruptum. 



Spikelets disarticulating above the glumes. 

 Awn included within the glumes, or wanting. 



Panicle rather lax, nodding 1. T. melicoides. 



Panicle rather dense, erect 2. T. wolfii. 



Awn exserted. 



Awn straight (see also T. montanum var. shearii) _ 3. T. orthochaetum. 

 Awn geniculate. 



Panicle dense, spikelike, sometimes slightly interrupted below; plants 



densely tufted 5. T. spicatum. 



Panicle loose and open to contracted, but not spikelike; plants in small 

 tufts or solitary. 

 Panicle relatively few-flowered, loose, lax or drooping, the filiform 



branches naked below; florets distant 4. T. cernuum. 



Panicle many-flowered, from rather loose to dense and interrupted; 

 florets not distant. 

 Panicle yellowish; spikelets mostly 3- or 4-flowered; introduced. 



8. T. FLAVESCENS. 



Panicle pale green, sometimes purplish-tinged; spikelets usually 

 2-flowered. 



Spikelets about 8 mm long 6. T. canescens. 



Spikelets 5 to 6 mm long 7. T. montanum. 



1. Trisetum melicoides (Michx.) Scribn. (Fig. 552.) Culms 50 

 to 100 cm tall; sheaths pubescent or scabrous; blades 2 to 8 mm wide, 

 scabrous, sometimes pubescent on the upper surface; panicle some- 

 what open, nodding, 10 to 20 cm long, the branches slender, ascend- 

 ing, lax or drooping, as much as 7 cm long, rather closely flowered 

 above the middle; spikelets scaberulous, 6 to 7 mm long; glumes 4 to 6 

 mm long, the second longer and broader; lemmas acute, 5 to 6 mm 

 long, rarely with a minute awn just below the tip, the rachilla and callus 

 hairs 1 to 2 mm long. 91 — River banks, lake snores, mostly in gravelly 

 ground, Newfoundland to Vermont, Michigan, and Wisconsin (fig. 553). 



