108 BULLETIN 772, IT. 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 Arena 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 Aim 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 Yasey, 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 
caiiescens Buckl., of the Western 
States, is a woodland grass with 
Trisetum cemuum Trim, 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 1 
narrow but rather loose panicles. 
