POACEAE. 



53 



Dioecious, seashore plant; spikelets 10-15 mm. 



long. P. macrantha. 



Perfect; spikelets 4-5 mm. long. P. pratensis. 



Lemma not webbed. 



Low seashore plant with narrow involute leaves 



and small panicle; spikelets close. P. confinis. 



Taller grass, not maritime, with flat or folded 



leaves; spikelets loose. P. nervosa. 



Plants tufted, without rootstocks. 



Lateral nerves ol lemmas prominent ; web present. P. trivialis. 



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. P. arctica. 



Panicle ample, spreading; spikelets 3-4 mm. 



long. P. triflora. 



Leaves flat, rather short, soft and flaccid. 



Panicle lax and spreading; spikelets 5-6 mm. 



long; florets not early deciduous. P. leptocoma. 



Panicle narrow, the rays usually erect; 



florets early deciduous. 



Lemma glabrous or nearly so. P. 



Lemma pubescent. P. 



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

 Nerves of the lemma pilose below. 



Alpine plant; leaf blades flat, green, broad. 

 Maritime plant; leaf blades narrow or 



folded, glaucescent. 

 Nerves of the lemma not pilose. 



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



highest mountains. 

 Leaves soft; panicle purple, very short; 



plants 510 cm. high. 

 Leaves rather rigid; panicle pale, narrow, 



elongated; plant 10-20 cm. high. 

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



grasses of rupestrine habitat. 

 Panicle close, erect; leaves flat. 



Lemmas pubescent at base; leaves 



rather narrow, sometimes folded. 

 Lemmas glabrous; leaf blades 



broader. 

 Panicles loose; leaves narrow, flat or 



involute. 



Ligules of the sterile shoots obsolete; 

 of the stem leaves short and trun- 

 cate. 

 Ligules well developed on all the 



leaves. 

 Rays of the panicle in about 5 



series; ligules 2-5 mm. long 

 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. 



bolanderi. 

 howellii. 



P. alpina. 



P. pachypholis. 



P. lettermani. 

 P. suksdorfii. 



P. sandbergii. 

 P. paddensis. 



P. multnomae. 



P. alcea. 



