No. 71. 

 POA ARCTIC A B. Br. Chlor. Melv. 288 (1823). 



Plant perennial from a. stoloniferous rootstock, usually purple in the inflorescence. 



Culm erect, or sometimes rather weak and geniculate bflow, smooth, 6 to 15 

 inches tall. 



Leaves of the culm usually 2 ; sheaths equaling or exceeding the internodes, smooth, 

 striate, usually rather close; blades narrowly linear, 1 to fi lines wide, 1 to 2 inches 

 long, hispidulous above or nearly smooth ; ligule 1 line long or less. 



Inflorescence a loose, ovate or oblong panicle 1 to 3 inches long; rays mostly in 

 pairs at the 5 to 7 nodes, slender, smooth, divided near the ends and bearing 2 to 4 

 spikelets on pedicels 2 to 3 Hues long. 



Spikelets obovate, turgid or sometimes spreading and flattened, 3- to 6-flowered, 

 2£ to 3 lines long; first empty glume ovate, acute or barely obtuse, carinate, thin, 

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

 1^ lines long; second empty glume broader, less acute, convex, smooth, 3-nerved, 1£ 

 lines long; floral glume ovate, obtuse or barely acute, convex, membranaceous above, 

 5-nerved, the two inner lateral nerves often obscure, pubescent on the lower half, 

 usually villous on the outer lateral nerves and midnerve, 1£ to 2 lines long; web at 

 the base about equaling the glume; palet linear-oblong, slightly bifid at the apex, 

 ciliate on the 2 keels, 1 to 1-| lines long; grain somewhat triangular, § line long; 2 

 lodiculesmore or less prominent, one usually broad and dentate and the other lanceolate. 



Plate LXXI: a, spikelet; b, empty glumes and floret partly dissected; c, first 

 empty glume; d, second empty glume; e, floral glume; /, pistil nearly mature. 1, 

 from Eocky Mountains in British Columbia; 2, Ungava Bay, Labrador; 3, Fort Con- 

 ger, Grinuell Land, Lieut. Greeley and D. L. Brainard, typical form; 4, Kelso Moun- 

 tain, Colorado. 



Alaska to Greenland and south in the Rocky Mountains to Colorado. This species 

 is distinct from P. cenisia All. in being smaller in size, having smoother rays and 

 smaller, fewer flowered spikelets. The floral glume in P. cenisia, is pubescent only on 

 the midnerve and outer lateral nerves, while in P. arctica it is pubescent throughout 

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



