164 



POACEAE 



34. AIRA L. Sp. PI. 63. 1753; Gen. PI. ed. 5. 31. 1754. 



Spikelets 2-flowered, disarticulating above the glumes, the hairy rachilla prolonged 

 behind the upper floret, this sometimes bearing a reduced floret ; glumes about equal, acute 

 or acutish. membranaceous ; lemmas thin, truncate and 2- to 4-4oothed at the summit, bearing 

 a slender awn from or below the middle, the awn straight, bent, or twisted, sometimes 

 absent from the lower floret. Low or rather tall annuals or usually perennials with shining 

 pale or purplish spikelets in narrow or open panicles. [A Greek name for a grass.] 

 Species about 35, in the temperate and cool regions of the world. Type species, Aira caesfitosa L. 



Plants annual. 

 Plants perennial. 



Panicle elongate, narrow, loose, the distant branches appressed; blades filiform, 



Panicle open or contracted but not elongate and loose. 

 Blades thin, flat; glumes longer than the florets. 



1. A. danthonioides. 



2. A. elongata. 



3. A. atropurhurea. 



liiaUCb null, lIciL, glHlllV.3 lung^i mciii i..._ ..^.^..^. r t 



Blades firm, narrow, becoming folded or involute; glumes about as long as or shorter than the upper 

 floret. 



Panicle narrow, compact, erect. 

 Panicle open, usually drooping. 



1. Aira danthonioides Trin. 

 Annual Hair-grass. Fig. 369. 



Aira danthonioides Trin. Mem. Acad. St. Petersb. VI. Math. 



Phys. Nat. 1: 57. 1830. 

 Deschampsia calycina Presl, Rel. Haenk. 1: 351. 1830. 

 Dcschampsia danthonioides Munro; Benth. PI. Hartw. 342. 



1857. 

 Deschampsia (jiacilis Vasey, Bot. Gaz. 10: 224. 1885. 



Annual; culms slender, erect, 15-60 cm. tall; blades 

 few, short and narrow; panicle open, 7-15 cm. long, 

 the branches capillary, stiff^ly ascending, naked below, 

 bearing a few spikelets toward the ends ; glumes 4-8 

 mm. long, acuminate, smooth except the keel, longer 

 than the florets ; lemmas smooth and shining, some- 

 what indurate. 2-3 mm. long, the base of the florets 

 and the rachilla pilose, the awns geniculate, 4-6 mm. 

 long. 



Open ground, from Alaska to Mexico, throughout our 

 region except in the higher mountains. June-Aug. Type 

 locality: western North America. 



4. A. holciformis. 



5. A. caespitosa. 



2. Aira elongata Hook. 

 Slender Hair-grass. Fig. 370. 



Aii-a elongata Hook. Fl. Bor. Am. 2: 243. pi. 228. 1840. 

 Deschampsia elongata Munro; Benth. PI. Hartw. 342. 1857. 

 Deschampsia elongata ciliata Vasey; Beal, Grasses N. Am. 2: 



371. 1896. 



Deschampsia elongata tennis Vasey; Beal, Grasses N. Am. 2: 



372. 1896. 



Perennial; culms slender, erect, 30-120 cm. tall; 

 blades flat, narrow, the basal clusters usually capillary; 

 panicle narrow, as much as 30 cm. long, the branches 

 slender, appressed; glumes 4-6 mm. long; lemmas 2 

 mm. long, similar to those of A. danthonioides, the 

 awns shorter. 



Open ground in the Transition Zone; Alaska to Montana 

 and south to southern California and Arizona. Mav-Tuly. Type 

 locality: islands of the Columbia River. 



