108 BULLETIN 772, TJ. S. DEPARTMENT OF AGRICULTURE. 



unequal, acute, awnless, the second usually longer than the first 

 floret; lemmas usually short-bearded at the base, 2-toothed at the 



apex, the teeth often awned, bear- 

 ing from the back below the 

 cleft apex a straight and in- 

 cluded, or usually bent and ex- 

 serted, awn. 



Tufted perennials with flat 

 blades and open or usually con- 

 tracted or spikelike panicles. 

 Species about 65, in the arctic 

 and temperate regions of both 

 hemispheres ; eight species in the 

 United States, mostly in the 

 mountains. 



Type species : Arena flavescens L. 



Trisetum Pers., Syn. PI. 1: 97. 1805. 

 Persoon describes 11 species. The 

 seventh species, T. pratense Pers., 

 based on Avena flavescens L., is chosen 

 as the type, because it is historically 

 the oldest species. 



Graphephorum Desv., Nouv. Bull. 

 Soc. Philom. Paris 2: 189. 1810. 

 Based on Aira melicoides Michx. 



The name Trisetum refers to 

 the three awns on the lemma of 

 many of the species, one from the 

 back and one from each of the 

 teeth. In two of our species, T. 

 melicoideum (Michx.) Scribn. 

 and T. wolfii Vasey, the awn 

 from the back is included within 

 the glume or is wanting. Trise- 

 tum spicatum (L.) Eichter (fig. 

 56) is found at high altitudes in 

 all the western mountains and is 

 widespread at high altitudes and 

 in the arctic regions of the North- 

 ern Hemisphere. It is an erect 

 grass with a spikelike, often 

 dark-colored panicle, the awn 

 exserted and bent. Trisetum 

 canes cens BuckL, of the Western 

 States, is a woodland grass with 

 narrow but rather loose panicles. Trisetum cernuum Trin., of the 

 Northwest, has broad flat blades and a loose open penicle, with lax 



FIG. 55. Koeleria cristata. 

 spikelet and floret, 



Plant, 

 X 5. 



X I 



