540 
CVII. GRA.MINEJS. 
[. Aira . 
genus Glyceria; but it does not naturally combine with them. Rhizome 
very long, branched, floating, jointed, sending from the joints fibrous 
radicles below, and cvlms above, a foot or more long, stout, with 
short broad leaves. Glumes with only a single nerve or midrib, 
thin and membranous, broadly oval, obtuse. Glumellas of a thick 
texture, brownish-green, white and diaphanous at the blunted ex- 
tremity. 
16. Aira Linn. Hair-grass. (Tab. VII. f. 15.) 
Panicle lax (rarely contracted). Spikelets laterally com- 
pressed, with 2 (or rarely 3 or only 1) perfect florets and some- 
times a neuter one which is usually rudimentary. Glumes 2, 
unequal, about as long as the florets , the outer 1 -nerved. Glu- 
mellas membranous and thin, hairy at the base ; the outer one 
awned at the back, with or without faint lateral nerves, toothed 
or entire or bifid but not setigerous at the end. Caryopsis 
glabrous. — Named from aipw, to destroy. This name was an- 
ciently applied to the Lolium temulentum (bearded darnel), on 
account of its injurious effects, and now to the present genus of 
Grasses, although it has little in common with it. 
* Outer glumella erose or toothed at the end. Caryopsis free. Neuter 
floret subulate. 
1. A. C(espit6sa L. (tufted II.) ; panicle diffuse, branches sca- 
brous, glumes slightly rough on the midrib, upper 3-ribbed’, 
florets hairy at the base rather longer than the glumes, awn 
straight inserted near the base of and seldom exceeding in 
length the outer glumella. — a. vulgaris ; sheaths of leaves rough, 
awn the length of the floret. E. B. t. 1453 : Pam. Gr. tt. 23, 
104. — S. brevifolia; radical leaves short, sheaths smooth, pa- 
nicle small, awn the length of the floret. Pam. Gr. t. 106. — 
y. longiaristata ; sheaths smooth, awn projecting one third be- 
yond the floret. Pam. Gr. t. 105. 
Moist shady places, and borders of fields, plentiful. — A and y. 
on the mountains. If. 6, 7. — Much tufted. Culms 2 — 4 ft. high. 
Leaves linear, acuminate, rough on the margin. Liyule long, acute, 
entire. Panicle large, silvery-gray or greenish, much branched, smaller 
and purplish in j8. Spikelets acute. Glumes unequal, lanceolate, sub- 
glabrous, rather acute, erose. Florets with a few longish hairs at the 
base, upper ones pedicellate ; their glumellas ovate, obtuse, erose, the 
outer one with 4 short teeth, the inner bifid. Var. A is frequently 
collected for the next species, from which it can only be certainly 
known by the position of the awn ; var. y. has sometimes but one 
fertile floret, when it is A. conglomerata Don. 
2. A. alpina L. (smooth Alpine H.) ; panicle subcoarctate, 
branches and pedicels perfectly or nearly smooth, glumes smooth 
on the midrib, upper 3-ribbed, florets as long as the glumes, 
