114 BULLETIN 772, U. S. DEPAKTMEKT OF AGRICULTURE. 
49. Aiea L. 
(Deschampsia Beauv.) 
Spikelets 2-flowered, disarticulating above the glumes, the hairy 
rachilla prolonged behind the upper floret as a stipe, this sometimes 
bearing a reduced floret; glumes about equal, acute 
or acutish, membranaceous; lemmas thin, truncate 
and 2 to 4 toothed at the summit, bearing a slender 
awn from or below the middle, the awn straight, bent, 
or twisted. 
Low or moderately tall 
annual or usually peren- 
nial grasses, with shining 
\ 1 1 P a k or P ur pli sn spikelets 
in narrow or open pani- 
cles. Species about 35, in 
the temperate and cool 
regions of both hemispheres, 6 of these 
being in the United States. 
Type species: Aira cacspitosa L. 
Aira L., Sp. PI. 63, 1753 ; Gen. PI., ed. 5, 31. 
1754. Fourteen species are described. The 
name was first used for a genus by Linnseus 
in his Flora Lapponica in 1737, where he 
describes four species. These four species 
are named in the Species Plantaruin : 7. A. 
spicata, 8. A. caespitosa, 9. A. fle.ruosa, 10. 
.1. montana. The first of these, A. spicata. 
is referred to Trisetum ; the other three be- 
long to Deschampsia, as recognized in most 
American botanies. The genus Aira, as 
accepted by Bentham and Hooker in the 
Genera Plantarum and by Hackel in the 
Naturlichen Pflanzenfamilien, is based upon 
the last two of the original Linngean 
Pig. 59. — Tall oat-grass, Arrhenathcrum elatius. Plant, X h ; spikelet and fertile floret, 
X 5. 
