MANUAL OF THE GRASSES OF THE UNITED STATES 



287 



Muhlenberg and may be assumed to Muhlenberg Herbarium described 

 be the same as the specimen in the under Aira pallens by Muhlenberg. 



57. TRISETUM Pers. Trisetum 



Spikelets usually 2-flowered,' sometimes 3- to 5-flowered, the rachilla pro- 

 longed behind the upper floret, usually villous; glumes somewhat unequal, 

 acute, the second usually longer than the first floret; lemmas usually short- 

 bearded at 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 peren- 

 nials (except Trisetum interruptum) , with flat blades and open or usually con- 

 tracted or spikelike shining panicles. Type species, Trisetum flavescens. Name 

 from Latin tri, three, and setum, bristle, alluding to the awn and two teeth 

 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. wolfi 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. orthochajetum. 



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. 386.) Culms 50 to 100 

 cm. tall; sheaths pubescent or sca- 

 brous; blades 2 to 8 mm. wide, sca- 

 brous, sometimes pubescent on the 

 upper surface; panicle somewhat open, 

 nodding, 10 to 20 cm. long, the 

 branches slender, ascending, 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; lem- 

 mas 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. % —River banks, Figure 386 _ Trisetum melicoides , Panicle , 

 lake shores, mostly in gravelly ground, glumes and floret, x 5. (Pringie, vt.) 



X 1; 



