AVENE.E. 



361 



Introduced on ballast ground, Philadelphia. 



74. (152). AiRA L. Sp. PI. 63 (1753). Asjwis Adans. Fam. 3: 

 496 (1763). Leplophoba Ehrh. Beitr. 4: 146 (1789). ProineiaX. c. 

 149(1789). Antimria \\xv\. Y\. Palerm. 1:92 (1845). Fiorinia 

 Pari. Fl. Ital. 1:232 (1848). Molineria 1. c. 236 (1848). Peri- 

 ballia Trin. Fund. Agrost. 133 (1848). Fussia Schur. Enum. PI. 

 Transs. 754 (1866). 



Spikelets 2-flowered, small, in a loose or rarely contracted pani- 

 cle with capillary rays; rachilla articulate, minutely hairy and not 

 at all or scarcely produced beyond the perfect flowers. Empty 

 glumes thinly scarious, nearly equal, acute; floral glume close above 

 them, shorter, thin and hyaline, finely pointed or shortly bifid, 

 with a fine dorsal twisted awn below the middle; palea 2-nerved, 

 hyaline, about as long as its glume. Styles short, distinct. Grain 

 enclosed and more or less adnate to the glume and palea. 



Delicate slender grasses, usually annuals with narrow blades. 



A small genus with 4-5 species, all of which are European, 

 though some of them are now widely disseminated in other temper- 



FlG. 63. — Aira caryopJiyllea. Spikelet. (Richardson.) 



ate regions. The genus formerly was made to include Deschamp- 

 sia, Airopsis, Corynepliorus, and others. It is nearly allied to 

 [vena, Isachne, Micraira, Ccelachne. 



