CHAPTER XXI 



Tribe IX. AVENEiE 



A MODERATELY large tribe of about 30 genera, found in 

 the cooler parts of the world. Spikelets 2- to several- 

 flowered, in open or contracted panicles or sometimes in 

 racemes; lemmas usually shorter than the glumes, usually 

 awned on the back or from between the teeth of a bifid 

 apex, the awn bent and often twisted, the callus and 

 usually the rachilla-joints hairy. Only a few of the genera 

 are found in America. In all these except Aira, an intro- 

 duced genus, there is a prolongation of the rachilla behind 

 the uppermost floret; and except in some species of Spheno- 

 pholis and in the American species of Kceleria the lemma is 

 awned. These genera are usually placed in Festucese, but 

 in all characters except the absence of the awn they show 

 affinity with the genera of Aveneae. 



Key to Genera of Avene^ 



A. Articulation below the glumes, these deciduous 

 with the whole or a part of the spikelet. 

 B. Glumes longer than the 2 florets, pubescent.. Notholcus 

 BB. Glumes shorter than the 2 or 3 florets, (Par. 238). 



glabrous or scabrous, the second widened 



above Sphenopholis. 



AA. Articulation above the glumes and between 

 the florets. 

 B. Lemma awnless or mucronate; inflorescence 



a spike-hke panicle; an erect perennial K(ELERIA. 



BB. Lemma awned. 



c. Rachilla not prolonged; spikelets 2-flow- 



ered; delicate introduced annuals Aira. 



cc. Rachilla prolonged behind the uppermost 

 floret. 



(208) 



