110 BULLETIN 772, U. S. DEPARTMENT OF AGRICULTURE. 
46. Sphenopholis 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: Aira obtusata Miehx. 
Reboulea Kunth, Rev. Gram. 1: 341, pi. 84, 1830, not Rebouillia Raddi, 1818. 
R. gracilis, the only species described, is the same as Aira obtusata Michx. 
Colobanthus (Trim) 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 pollens), the first of two species mentioned by 
Trinius, the other being Aira obtusata 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 obtusata (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. lobata (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. fatua, 
and A. pratensis. The other species are now referred as follows: A. sibirica to 
iGen. PI. 99. 1837. 2 Hitchcock, Contr. TJ. S. Nat. Herb. 15:87. 1910. 
