No. 71. 

 POA ARCTIC A U. I'.r. Cliloi. M.-lv. 288 (1823). 



riiuil pcrciiiiiiil IVoiii 1) stoloiiilci'ous niotstock, iisiially iiiirplf in the inflorescence. 



Ciihii iTwt, or sometimes rather weak and {j:cnicnlatc be low, smooth, <! to 1~> 

 inches tall. 



Liavc.1 ol" thecnlm usually 2 ; sheaths equaling or exceeding the internodes, smooth, 

 .striate, usually rather close; blailes narrowly linear, 1 to U lines wide, 1 to 2 inches 

 lonjr, hispiduhms above or nearly smooth; liffule 1 line hius" or less. 



Iii/lorencrure a loose, ovate or ohlonj; ])ani(;le 1 to li inches lonj^; rays mostly in 

 l)airs at the 5 to 7 nodes, slender, smooth, divided near the ends and hearing; 2 to 4 

 spikelets on pedicels 2 to 3 lines lonfj. 



Spihelftx obovate, turgid or sometimes spreading and flattened, .5- to li-llowcred, 

 2i to 3 lines long; first empty glume ovate, acute or l)aiely obtuse, earinate, thin, 

 smooth, usually purjdish throughout, 1-nerved or rarely 3-nerved at the base, 1 to 

 14 lines long; second em])ty glume broader, less acute, convex, smooth, S-nerved, 1.^ 

 lines long; floral glume ovate, obtus<^ or barely acute, <;onvex, membi'anaeeous above, 

 o-nerved, the two iTuier lateral nerves often obscure, pubescent on th(^ lower half, 

 usually villous on the outer lateral nerves and midnerve, 1^ to 21ines long; web at 

 the base about ei|ualing the glume; palet linear-oblong, slightly bitid at tlieai)ex, 

 ciliate on the 2 keels, 1 to 1.^ lines long; grain somewhat triangular, rj line iong; 2 

 lodiculesmoreor lessprominent, oneu.sually bioad and dentate and the other lanceolate. 



Plate LXXI: a, si)ikelet; //, empty ulunies and lloict partly dis.sected; c, first 

 iemi)ty glume; fl, second emjity glume; c, tloral glume; ./', pistil nearly mature. 1, 

 from Ivocky INIountains in British Columbia; 2, lTnga\a Bay, L;ibrador; 3, Fort Con- 

 ger, Grinnell Land, Lieut. Greeley and D. L. Hrainard, typical form; 4, Kelso ^foun- 

 tain, Colorado. 



Alaska to Greenland and south in tlui Rocky Mountains to Colorado. This sjjecies 

 is distinct from P. ccnixia All. in being sm;iller in size, having smoother rays and 

 smaller, fewer flowered spikelets. The tloial glume in /'. ccnma is jjubescent only on 

 the midiu'rve ami outer lateral nerves, while in P. urcfica it is pubescent throughout 

 below. Probably Fig. 4 should bo excluded from this species. 



