POACEAE. 



53 



P. macrantha. 

 P. pratensis. 



P. confinis. 

 P. nervosa. 

 P. trivialis. 



P. arctica. 

 P. triflora. 



P. leptocoma. 



P. bolanderi. 

 P. howellii. 



Dioecious, seashore plant ; spikelets 10-15 mm. 



long. 

 Perfect; spikelets 4-5 mm. long. 

 Lemma not webbed. 



Low seashore plant with narrow involute leaves 



and small panicle; spikelets close. 

 Taller grass, not maritime, with flat or folded 

 leaves; spikelets loose. 

 Plants tufted, without rootstocks. 



Lateral nerves ot lemmas prominent; web present. 

 Lateral nerves of lemmas not prominent. 

 Web present at base of lemma. 



Leaves flat or folded, not soft and flaccid. 



Panicle short pyramidal; spikelets 6-7 mm. 



long; low alpine plant. 

 Panicle ample, spreading; spikelets 3-4 mm. 

 long. 

 Leaves flat, rather short, soft and flaccid. 



Panicle lax and spreading; spikelets 5-6 mm. 



long; florets not early deciduous. 

 Panicle narrow, the rays usually erect; 

 florets early deciduous. 

 Lemma glabrous or nearly so. 

 Lemma pubescent. 

 Web absent, no tuft of hairs at base of lemma. 

 Nerves of the lemma pilose below. 



Alpine plant ; leaf blades flat, green, broad. P. alpina. 

 Maritime plant; leaf blades narrow or 



folded, glaucescent. P. pachypholis. 



Nerves of the lemma not pilose. 



Stems low, 5-20 cm. high; grasses of the 

 highest mountains. 

 Leaves soft; panicle purple, very short; 



plants 5-10 cm. high. P. lettermani. 



Leaves rather rigid ; panicle pale, narrow, 



elongated; plant 10-20 cm. high. P. suksdorfii. 



Stems taller, usually 20-40 cm. high, mostly 

 grasses of rupestrine habitat. 

 Panicle close, erect; leaves flat. 



Lemmas pubescent at base; leave's 



rather narrow, sometimes folded. P. sandbergii. 

 Lemmas glabrous ; leaf blades 



broader. P. paddensis. 



Panicles loose; leaves narrow, flat or 

 involute. 

 Ligules of the sterile shoots obsolete; 

 of the stem leaves short and trun- 

 cate. P. multnomae. 

 Ligules well developed on all the 

 leaves. 

 Rays of the panicle in about 5 



series; ligules 2-5 mm. long P. alcea. 



Rays of the panicle in fewer 

 series; ligules 1—2 mm. long. 

 Panicle close; . glumes firm; 



blades flat. P. saxatilis. 



Panicle loose; glumes thin; 



blades involute. P. gracillima. 



