GENERA OF GRASSES OF THE UNITED STATES. 
107 
lemmas somewhat scarious and shining, the lowermost a little longer 
than the glume, obscurely 5-nervecl, acute or short-awned, the awn, 
if present, borne just below the apex. 
Annual or perennial, slender, low or rather tall grasses, with nar- 
row blades and spikelike panicles. Species about 20, in the temperate 
regions of both hemispheres; two species in the United States, one 
native and one introduced. 
Type species: Aira cristata L. 
Koeleria Pers., Syn. PI. 1:97. 1805. Persoon describes five species, K. gra- 
cilis, K. cristata, K. tuberosa, K. phleoides, and K. villosa. Of these, K. cristata 
and K. phleoides were described by Linnseus, the first under Aira, the second 
under Festuca. The first of these is selected as the type, as it has priority of 
position in the Species Plantarum. 
Airochloa Link, Hort. Berol, 1 : 126. 1827. Six species are included. Koeleria 
cristata, upon which the first species is based, is taken as the type. 
Brachystylus Dulac, Fl. Hautes Pyr. 85. 1867. Based on " Koeleria Pers." 
Recently a monograph of Koeleria was published by Dornin 1 in which many 
species were described. Several of these were based upon material from the 
United States but appear to be only forms of the widely distributed K. cristata. 
Koeleria cristata (L.) Pers. (fig. 55) is the only species native in 
North America. This is a common constituent of grassland on prai- 
ries, plains, and in open woods from Ontario to British Columbia and 
south to northern Mexico. It is a cespitose perennial, with slender, 
erect culms a foot or two high, with a pale, shining, densely flowered 
panicle 2 to 5 inches long. The species varies much, but the forms, 
except K. cristata longifolia Vasey, of California, with longer blades 
and larger, more open panicles, can not be distinguished as varieties. 
The slender form, of the semiarid plains and foothills of the West, 
is held by some as distinct and called K. gracilis Pers. The 
spikelets of K. cristata are mostly 2 or 3 flowered, with a slender 
prolongation of the rachilla, and the lemmas are acute or mucronate, 
but not awned. The habit suggests a species of Poa, from which 
genus it is distinguished by its mostly 2 or 3 flowered spikelets, acute 
lemmas, and the culm puberulent below the panicle. A second 
species, K. phleoides (Vill.) Pers., a low annual with short-awned 
lemmas, is introduced from Europe in a few localities. Hackel (Nat. 
Pflanzenfam.) places Koeleria in the Festucea3, but South American 
and Old World species of Koeleria, with lemmas awned below the 
apex, as well as the shining culm and spikelets of K. cristata, show 
clearly an affinity to Trisetum. For this reason the genus is here 
placed in Aveneae, although the glumes do not exceed the florets as 
they do in nearly all the Aveneae. 
Koeleria cristata is a good forage grass and is a constituent of 
much of the native pasture throughout the Western States. 
45. Trisetum Pers. 
Spikelets usually 2-flowered, sometimes 3 to 5 flowered, the rachilla 
prolonged behind the upper floret, usually villous ; glumes somewhat 
iMonographie der Gattung Koeleria. 1907. 
