GENERA OF GRASSES OF THE UNITED STATES. 107 



lemmas somewhat scarious and shining, the lowermost a little longer 

 than the glume, obscurely 5-nerved, 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. yra- 

 cilis, K. cristata, K. tuberosa, K. phleoides, and K. villosa. Of these, K. cristata 

 and K. phleoides were described by Linnaeus, 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 Domin 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 Yasey, 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. grocilis 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. 

 Pfl anzenf am. ) places Koeleria in the FestuceaB, 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 



1 Monographic der Gattung Koeleria. 1907. 



