48 Graminaceae 
narrow, keeled, acute, awnless. Lemma shorter than the glumes, wide, delicately hyaline, 
awned or awnless; awn slender, twisted, attached below or sometimes above the middle 
of the lemma. Palet very thin, not over 14 as long as the lemma, often very minute 
or none. Stamens 1|—-3. Stigmas plumose. Grain free. (Gk. agros=a field; from 
the habitat.) 
A. Rachilla prolonged behind the palet. 
B. Spikelets 3 mm. long, usually purple; rachilla extending 0.6—1.5 mm. beyond 
the palet; ligule 2 mm. long. C. E 
A. aequivalvis Trin. 
BB. Spikelets 2 mm. long, usually pale; rachilla extending 0.3—0.5 mm. beyond 
the palet; ligule 6 mm. long. C. E. 
A. thurberiana Hitch. 
AA. Rachilla not prolonged behind the palet. 
C.  Palet evident, 2-veined.. 
D.  Palet 1% as long as the lemma or longer; panicle close, spike-like. 
E. Glumes scabrous on keel and back; lemma !/% as long as the glumes; pan- 
icle contracted, either lobed or verticillate. E. (A. verticillata.) 
A. stolonifera L. (Creeping Bent-grass) 
EE. - Glumes scabrous on keel but smooth on back; lemma at least 2/3 as long 
as the glumes; panicle more open. 
F. Plants with extensive creeping short-leaved stolons; panicle 2.5—5 cm. 
long. E. A. depressa Vas. 
FF. Plants without stolons; panicle mostly larger. 
G. Spikelets 2—3 mm. long; panicle 5—30 cm. long; plants 2—15 
dm. high, with rootstocks, not alpine. W. E. 
A. alba L. (Red-top) 
GG. Spikelets 1.5—-2 mm. long; panicle 2—8 cm. long; plants |—4 
dm. high, without rootstocks, alpine. W. C. E. 
A. humilis Vas. 
DD. Palet 14 as long as the lemma; panicle either close and spike-like or open. 
: A. densiflora, Vas. (Dense-flowered Bent-grass) | 
CC. Palet none, or a small veinless scale. 
H. Plants spreading by rootstocks. 
I. Hairs at base of lemma |—2 mm. long. U. E. (A. pringlei; A. hallii 
pringlei. ) A. hallii Vas. 
IJ. Hairs at base of lemma minute, or none. W.C. E. (A. pallens foliosa; 
A. diegoensis. ) A. pallens Trin. 
HH. Plants tufted, without rootstocks. 
J. Panicle narrow, rather close. 
K. Lemma-awn exserted. 
L. Glumes awn-pointed; panicle narrow and rather compact. W. E. 
A. microphylla Steud. 
LL. Glumes merely acute; panicle more open and vevtcillaie: [Gaia 2 
(A. virescens of How. FI.) 
A. ampla Hitch. 
KK. Lemma awn included or none. 
M. Spikelets 4—5 mm. long. W. 
A. occidentalis LS. & M. 
MM. Spikelets 2—2.5 mm. long. 
N. Panicle 3—6 cm. long; plant low, alpine. W.C. E. (A. va- 
rians. ) A, rossae Vas. 
an 
