108 Chase — Notes on Genera of Pamcece. PV . 



Articulation below the spikelet-bearing branchlets. 

 A single bristle produced beyond the solitary spikelets. 

 First glume present ; second glume and sterile lemma 



acuminate; fruit not acuminate . . 36. Chamaeraphis. 

 First glume usually obsolete, second glume minute, 



sterile lemma and fruit long-acuminate . 37. Paratkeria. 

 Bristles numerous below each spikelet or cluster of 

 spikelets. 

 Bristles not united at base, usually slender, often plu- 

 mose 38. Pennisetum. 



Bristles more or less united at base into a bur-like 



pseudo-involucre 39. Cenchrus. 



Articulation at the junction of the primary branches with 



the main axis 40. Plagioselum. 



Spikelets either sunken in the cavities of a corky axis or sur- 

 rounded by a sheath or by involucre-form bracts. 

 Spikelets sunken in the cavities of the flattened corky axis, this 

 disarticulating at maturity with the spikelets attached. 



41. Stenotaphrum. 

 Spikelets not sunken in a corky axis. 

 Spikelets in small spikes, these surrounded by rigid sheaths. 



42. Xerochloa. 

 Spikelets solitary, subtended by two glume-like bracts, these 



placed cross- wise to the spikelet* 43. Odontelytrum. 



Spikelets not all alike. 



Plants monoecious or polygamous, that is with the different kinds 

 of spikelets on one plant. 

 Spikelets all perfect, but those of the aerial panicle not perfect- 

 ing grains; the fruitful spikelets cleistogamous, borne on 



subterranean branches 44. Amphicarpon. 



Spikelets not all perfect. 

 Spikelets hermaphrodite and sterile. 



Spikes several, crowded on a leaf-like axis . . 45. Phyllorachis. 



Spike solitary 46. Thuarea. 



Spikelets unisexual. 



Inflorescence paniculate; fruit bony-indurated. 



Panicles terminal on culms or leafy branches, pistil- 

 late spikelets above, staminate spikelets below, 



in same panicle 47. Olyra. 



Panicles all axillary or axillary and terminal ; the 

 terminal when present wholly staminate. 

 Fruit laterally compressed, conspicuously gibbous 



on upper dorsum 48. Lithachne. 



Fruit dorsally compressed, lanceolate . 49. Raddia. 

 Inflorescence of spike-like racemes. 



Raceme solitary ; spikelets geminate, a pistillate and a 



staminate forming a pair ... . . 50. Diandrolyra. 



* Taken from Hackel's description. We have not yet seen the plant. 



