GRASS FAMILY 73 



-eadiug 



usually acuminate or very acute; cobweb scant or sometimes none. 

 Spikelets manv, light green; branches of the inflorescence numerous, the- 



lower in S's^ or 4's. or 5's; rootstock creeping. ITT. PL.\TYPnYLLAK. 



Spikelets few, usually more or less purple, except in P. Icptocoma; branches 

 of the inflorescence few, the lower usually in 2's, rarely m 3 s. spikclet- 

 bearing towards the ends. I'V. Keflexae. 



Intermediate nerves of the lemma faint or obsolete. tt ^-^ 



Stem compressed; lemma obtuse. . V. Comphp-ssae. 



Stem not compressed; lemma acute or acununate. _ 



Branches of the panicles reflexed; rootstock creepmg. \ I. Apertae. 

 Branches of the ]>anicles not reflexed. VII. Tkiflorae. 



^ Spikelets^ rounded at the base; empty glumes very broad and their keel strongly 

 arched; low tufted perennials, with short open panicle and broad leaves. 



VIII. Alpinae. 



Spikelets acute at the base; empty glumes narrower, not strongly arched on their 



Plants with horizontal creephig rootstocks; not bunch-grasses. ^ 



Spikelets strongb" compressed; lemma strongly keeled, ^strongly o-nerved,. 



conspicuously scabrous; glumes very acute. IX. \\ ueeleuianae. 

 Spikelets not strongly compressed; lemma neither strongly compressed 



nor strongly nerved (except in F. p^a/msi/ormis), not conspicuously 



Lemma acununate, dark purple; innovations extra vaginal. 



X. Phoemceae. 



Lemma obtuse or acutish, green or merely tinged with purple; innova- 

 tions both extra- and intravaginal. XI. Akidae. 

 Plants without extra vaginal rootstocks; densely tufted bunch-grasses. 



Lemma 3-4 mm. long. , , . ^ ... -i i *^. 



Low alpine plants, with narrow panicles of few purplish spikelets, 



lemma ovate. . -XII. Rcpicol.\e. 



Slender plants. 4-5 dm. high, with open panicles; lemma narrowly 

 lanceolate in side-view. XIII. Multnomae. 



Lemma 5 mm. long or more; plants comparatively robust. 



Spikelets decidedly flattened; lemma acute and keeled on the back. 

 Pubescence on the nerves of the lemma, if any. not stronger than 



on the internerves; flowers perfect. 

 Inflorescence dense and spike-like. XIV. Lfiles. _ 



Inflorescence open; branches s pikelet-bearing towards their 

 ends ^V. Gracillimae. 



Pubescence "of the nerves of the lemma villous or pilose, that of the 



internerves none or almost none; plants dioecious. 



XVI. Fexplerianae. 



Spikelets little flattened; lemma rounded on tlie backs towards the 

 apex, almost straight, obtuse. XV IL Buckley anae. 



I. Annuae. 



Low, 1-2 dm. liigh; branches of the panicle spreading. 1. P. annua. 



Taller, erect. 2-5 dm. high; branches of the panicle erect. 2. P. Bigelotxi. 



II. Pratenses. 



Lemma 3-4 mm. long; ligule truncate. 3. P. pratensis. 



Lemma 5 mm. long; ligule not truncate. 4. F. rhizomata. 



III. Pl.\typhyll,\e. 



5. p. occidenlaUs, 



Ligules truncate or abruptly acute. 



Ligules lanceolate. long attenuate. b. i". cantaa. 



IV. Reflexae. 



Cobweb present but often scant. -y d 7 , 



Lemmas obtuse; cobweb dense. 7. i-'. lanaia. 



Lemmas acute or acuminate; cobweb scant. ^ ^ , ^ ^ , 



Internerves of the lemma more or less pubescent, at least below. 



Spikelets 3-4-flowered; stem-leaves usually folded or involute; plant usually 

 less than 3 dm. high, tufted. . , * 



Internerves of the lemma short-pubescent below; leaves fihform, mvolute; 



those of the sterile shoots usually arcuate. 8. P. cenisia. 

 Internerves of the lemma long-hairy, at least below; leaves 1-2 mm. wide, 



usually conduplicate, rather firm. 

 Plant low, 1-3 dm. high, usually cespitose; lemma acute. 



9, P. arctica. 



Plant tall, 3-5 dm. high, not cespitose, with a creeping rootstock; 

 floral glmnes acuminate. 10. P. longipila. _ 



Spikelets 5-7-flowered; leaves all flat. 3-4 mm. wide; stem fully 3 dm. high. 



11. P. callichToa, 

 's of the lemma elabrous; plants with creeping rootstocks. 

 ediate nerves of the lemma pubescent; plant 3 dm. or less hii 

 mostlv basal, firm; stem-leaves 1-2. usually conduplicate. 



12. F. pudica. 



