292 MISC. PUBLICATION 200, U. S. DEPT. OF AGRICULTURE 



56. AIRA L. 



(Aspris Adans.) 



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



not prolonged; glumes boatshaped, about equal, 1-nerved or obscurely 

 3-nerved, acute, membranaceous orsubscarious; 

 lemmas firm, rounded on the back, tapering 

 into 2 slender teeth, bearing on the back below 

 the middle a slender geniculate twisted usually 

 exserted awn, this sometimes wanting in the 

 lower floret or reduced ; callus minutely bearded. 

 Delicate annuals with lax, subfiliform blades 



Fl ^Aam5i?Ja«ptfoiS n ° f and P en or contracted panicles of small spike- 

 lets. Type species, Aira praecox. Aira, an 



old Greek name for a weed, probably darnel. Weedy grasses of no 



economic importance, introduced from Europe. 



Figure 578. — Deschampsia holciformis. Panicle, X 1; 

 glumes and floret, X 5. (Bolander, Calif.) 



Figure 579.— Aira prtrecor* 

 Panicle, X 1; glumes and 

 floret, X 5. (Amer. Gr. 

 Nat. Herb. 375, Del.) 



Figure 580.— Distribution of 

 Aira praecox. 



Panicle dense, spikelike 1. A. praecox. 



Panicle open. 



Lower floret with awn as long as that of the upper floret 



2. A. CARYOPHYLLEA. 



Lower floret awnless or nearly so 3. A. capillaris. 



1. Aira praecox L. (Fig. 579.) Culms tufted, 10 to 20 cm tall, 

 usually erect; panicle narrow, dense, 1 to 3 cm long; spikelets yellow- 

 ish, shining, 3.5 to 4 mm long; lemmas with awns 2 to 4 mm long, 

 that of the lower floret the shorter, o — Sandy open ground, along 

 the coast, New Jersey to Virginia; Vancouver to California (fig. 580).. 



