58 Graminaceae 
rudimentary; panicle usually loose and spreading, rarely narrow and spike-like; rachilla 
jointed between the flowers, glabrous or rarely sparingly pilose. Glumes membranous, 
acute or obtusé, persistent, |—-3-veined. Lemma membranous or herbaceous, delicately 
scarious-margined, mostly scarious-tipped, acute or obtuse, keeled, awnless, usually sur- 
rounded by a few woolly hairs, 5 (rarely 7-)-veined; veins usually bent inward near 
the apex, dorsal or marginal ones usually soft-hairy. Palet 2-toothed. Stamens Wears | 
Grain ovoid or oblong or almost linear, compressed, rarely with a wide groove, glabrous, 
enclosed. (Gk. poa=grass or fodder in general.) 
A. Lemma with long spider-web-like hairs at base. -- Group 1 (p96) 
AA. Lemma «without spider-web-like hairs at base. 
Group 2 (p. 59) 
B: Lower gltime 1|-veined. 
BB. Lower glume 3—5-veined. Group 3 (p. 60) 
GROUP | 
A. Stem flat, 2-edged; panicle |—4 cm. long, flat. W. E. 
P. compressa L. (Canada Blue-grass) 
AA. Stem terete; panicle often smaller, rarely flat. 
B. Lemma smooth or merely roughish. 
C. Panicle 2.5—7.5 cm. long; palet 2-toothed. E. 
P. kelloggii Vas. 
CC. Panicle 10-——15 cm. long; palet obtuse. 
D. Leaf-sheath exceeded by the internode; panicle-branches smooth. W. ES 
(P. bolanderi chandleri.) 
P. bolanderi Vas. 
DD.  Leaf-sheath exceeding the internode; panicle-branches scabrous. E. 
P. subtrivialis Rydb. 
BB. Lemma pubescent on the back at least on the veins or on its lower half. 
E. Lower glume |-veined. 
F. Lower 2—3 nodes of the panicle. usually with more than 3 rays. 
G. Leaf-sheath rough. 
H. Spikelets 34.5 mm. long; lemma 2.5—3 mm. long. W. 
P. trivialis L. (Rough Meadow-grass) 
HH. Spikelets 6.5——7.5 mm. long; lemma 4—5 mm. long. W. 
P. occidentalis V. & S. (Western Blue-grass) 
GG. _Leaf-sheath smooth. 
I. Upper ligule 1.5 mm. long; rootstocks present, hence stems not tufted. 
\\/ Gas P. pratensis L. (Kentucky Blue-grass) 
II. Upper ligule 4 mm. long; rootstocks none, hence stems tufted. W. 
P. howellii V- & S. 
FF. Lower 2—3 nodes of the panicle usually 2—3-rayed. 
J. Leaves not soft and flaccid, more or less folded lengthwise. C. : 
P. arctica R. Br. 
JJ. Leaves soft and flaccid, flat. 
K. Spikelets 3—4 mm. long; plant 5—-7 dm. high. W. C. E. 
P. leptocoma Trin. (Mountain Blue-grass) 
KK. Spikelets 56 mm. long; plant 1—3.5 dm. high. E. 
P. reflexa V. & S. (Nodding Blue-grass) 
EE. Lower glume 3—5-veined. 
L. Seashore plant, dioicous; spikelets 10—15 mm. long. W. 
; P, macrantha Vas. 
LL. Not particularly a seashore plant; spikelets perfect, 3—5 mm. long. 

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