198 A TEXT-BOOK OF GRASSES 



PF. Inflorescence an open or contracted 

 but not densely cylindrical pan- 

 icle; glumes not compressed- 

 carinate and ciliate. 

 G. Glumes saccate at base; lemma 

 long-awned; inflorescence con- 

 tracted, shining; annuals Gastridium. 



GG. Glumes not saccate at base. 



H. Lemma bearing an awn several 

 times its length; annuals 



with open panicles Apera. 



HH. Lemma short-awned, or awn- 

 less, the palea often reduced 



or wanting Agrostis 



DD. Glumes as long as, or shorter than the (Par. 234). 



lemma. 

 E. Lemma bearing a tuft of hairs at 

 base from the short callus. 



F. Lemma and palea thin Calamagrostis 



FF. Lemma and palea chartaceous. (Par. 235). 

 G. Panicles spike-like; rachilla pro- 

 longed Ammophila 



GG. Panicles open; rachilla not pro- (Par. 236). 



longed Calamovilfa. 



EE. Lemma without hairs at base. 



F. Palea apparently l-nerved, the 2 

 nerves close together; rachilla 



prolonged; panicle open Cinna. 



PF. Palea distinctly 2-nerved; rachilla 

 not prolonged. 

 G. Nerves of lemma densely silky. . Blepharo- 

 GG. Nerves of lemma not silky. [neuron. 



H Fruit not inclosed in the 

 lemma and palea, seed usually 

 also loose in the pericarp, 

 this opening at maturity. . . . Sporobolus. 

 HH. Fruit inclosed in the lemma 

 and palea; the seed also 

 inclosed in the pericarp at 

 maturity and grown to it; 

 panicles spike-like in our 

 species. 

 I. Panicles short, partly in- 

 closed in the upper sheath; 

 sparingly introduced from 



the Old World Heleochloa. 



n. Panicles elongated; tall per- 

 ennials of Arizona and 

 southward Epicampes. 



