110 BULLETIN 772, U. S. DEPARTMENT OF AGRICULTURE. 



46. SPHEXOPHOLIS Scribn. 

 (Eatonia of authors, not Raf.) 



Spikelets 2 or 3 flowered, the pedicel disarticulating below the 

 glumes, the rachilla produced beyond the upper floret as a slender 

 bristle ; glumes unlike in shape, the first narrow, acute, 1-nerved, the 

 second broadly obovate, 3 to 5 nerved, somewhat coriaceous; lemmas 

 firm, scarcely nerved, awnless, the first a little shorter or a little 

 longer than the second glume. 



Perennial grasses, with usually flat blades and narrow panicles. 

 Species four, in the United States, extending into Mexico and the 

 West Indies. 



Type species: Aim obhifuita Miehx. 



Reboulea Kunth, Rev. Gram. 1: 341, pi. 84, 1830, not Rebouillia Raddi, 1818. 

 A', gracilis, the only species described, is the same as Aira obtusata Michx. 



Colobanthus (Trin.) Spach. Suites Buff. 13: 163, 1846, not Bartl., 1830. 

 Trinius applied the name to a section of Trisetum. The type is Koeleria penn- 

 sylvanica DC. (Sphenopholis pallens), the first of two species mentioned by 

 Trinius, the other being Aira obtiisata Michx. 



Sphenopholis Scribn., Rhodora 8 : 142. 1906. A new name is proposed for the 

 group of grasses then known as Eatonia, and the type species is designated. 

 Scribner showed that the original description of Eatonia Raf. could not apply 

 to the genus as later described by Endlicher. 1 The type species of Eatonia Raf. 

 proves to be Panicum virgatum. 2 The genus Sphenopholis was revised by Scrib- 

 ner in the above-mentioned paper. 



One species, Sphenopholis obtwata (Michx.) Scribn. (fig. 57), is 

 widespread, but not very abundant, throughout the eastern half of 

 the United States. In the western portion of its range the panicle is 

 condensed and spikelike (var. lolata (Trin.) Scribn.). All the 

 species are forage grasses, but they are usually not abundant enough 

 to be of much importance. 



47. AVENA L., oats. 



Spikelets 2 to several flowered, the rachilla bearded, disarticulating 

 above the glumes and between the florets ; glumes about equal, mem- 

 branaceous or papery, several-nerved, longer than the lower floret, 

 usually exceeding the upper floret ; lemmas indurate, except toward 

 the summit, 5 to 9 nerved, bidentate at the apex, bearing a dorsal bent 

 and twisted awn (this straight and reduced in Avena sativa). 



Annual or perennial, low or moderately tall grasses, with narrow or 

 open, usually rather few-flowered panicles of usually large spikelets. 

 Species about 55, in the temperate regions; only a few in the Western 

 Hemisphere; 7 species in the United States, only 2 being native. 



Type species : Avena sativa L. 



Avena L., Sp. PI. 79, 1753; Gen. PI., ed. 5, 34. 1754. Linnaeus describes 10 

 species, 3 of which are now retained in Avena. These are A. sativa, A. fatiia, 

 and A. pratensis. The other species are now referred as follows : A. sibirica to 



. PI. 99. 1837. 2 Hitchcock, Contr. U. S. Nat Herb. 15:87. 1910. 



