198 A TEXT-BOOK OF GRASSES 



FF. 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. 



GO. 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. 



BE. Lemma without hairs at base. 



F. Palea apparently 1-nerved, the 2 

 nerves close together; rachilla 



prolonged ; panicle open CINNA. 



FF. 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. 



