GENERA OF GRASSES OF THE UNITED STATES. 



149 



69. SPOROBOLUS R. Br. 



Spikelets 1-flowered, the rachilla disarticulating above the glumes; 

 glumes awnless, usually unequal, the second often as long as the spike- 

 let; lemma membranaceous, 1-nerved, 

 awnless; palea usually prominent and 

 as long as the lemma or longer; seed 

 free from the pericarp. 



Annual or perennial grasses, with 

 small spikelets in open or contracted 



PIG. 84. Smut-grass, Sporobolus berteroanus. Plant, X i ; spikelet and floret, X 5. 



