PANICE^ 177 



sisting of the chartaceous fertile lemma and palea inclos- 

 ing a caryopsis the covering of which is thin. The genus 

 Amphicarpon is peculiar in having 2 kinds of spikelets, 

 ordinary spikelets in a terminal panicle, and underground 

 cleistogamous spikelets borne on short subterranean 

 branches that appear like rhizomes. Only the latter bear 



seed. 



Key to the Genera of Panice^ 



A. Spikelets not all alike. 



B. Spikelets all perfect, but those of the aerial 

 panicle not perfecting grains; the fruitful 

 spikelets cleistogamous, borne on sub- 

 terranean branches. Florida to New Jersey. Amphicarpon. 

 BB. Spikelets not all perfect, the inflorescence 

 bearing pistillate spikelets above and 

 staminate spikelets below; panicles ter- 

 minating the branches; blades broad, 



eHiptical. Florida Olyra. 



AA. Spikelets all alike. 



B. Spikelets sunken in the cavities of the 



flattened corky axis Stenotaphrum 



BB. Spikelets not sunken in the rachis. (Par. 223). 



c. Spikelets subtended or surrounded by 1 to 

 many bristles (sterile branchlets), these 

 distinct or more or less connate, forming 

 an involucre. 

 D. Bristles persistent, spikelets deciduous.. Ch^tochlo a 

 DD. Bristles falhng with the spikelets at (Par. 220). 



maturity. 

 E. Bristles not united at base, usually 



slender, often plumose Pennisetum 



EE. Bristles more or less united into a bur- (Par. 221). 



like involucre Cenchrus 



cc. Spikelets not subtended by bristles. (Par. 222). 



D. Fruit cartilaginous-indurated, not rigid, 



papillose, usually dark-colored, the 



lemma with more or less prominent 



white hyaline margins not inroUed. 



E. Fruiting lemma boat-shaped, the 



hyaline margins narrow. Florida 



to Louisiana Anth^nantia 



ee. Fruiting lemma convex, the hyaline 

 margins broad. 

 F. Fruit lanceolate-acuminate; second 

 glume and sterile lemma long- 

 silky. Florida to Arizona Valota. 



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