DESCRIPTIONS OF TRIBES AND GENERA. 71 



IV. Empty glumes three, and $ flower one, 

 or a flowering glume with $ flower instead 

 of the third empty glume. 

 1. First and second empty glumes with- 

 out a distinct callus, awnless. 



* Flowering glumes without lateral 

 appendages or pits at the base. 



62. Panicum. 



** Flowering glume with membrana- 

 ceous appendages or pits at the 



base 63. Ichnanthus. 



2. First empty glume very small, awnless, 

 the second apparently distant from the 

 first on account of a conical or pedicel- 

 like callus, and like the third (flower- 

 ing glume of the $ floret) more or less 

 awned between the cleft apex. 



64. Tricholaena. 

 3. First and second empty glumes awned. 



* First empty glume without any dis- 

 tinct callus. . . .65. Oplismenus. 



** First empty glume with a pointed, 



pedicel-like callus. 66. Chaetium. 



/?. Spikelets single or in pairs, subtended by an 



involucre consisting of from one to many bristles 



or spines (sterile branches) which are sometimes 



grown together. 



I. Spikelets falling at maturity, bristles per- 

 sistent 67. Setaria. 



II. Involucral bristles falling off with the spike- 

 lets at maturity (cultivated forms excepted). 

 1. Bristles numerous, rigid, thickened at 

 the base, frequently grown together. 



68. Cenchrus. 



2. Bristles usually numerous, apparently 

 whorled, delicate, not thickened at the 

 base, often plumose. 69. Pennisetum. 

 3. Involucral bristles numerous, forming 

 a paniculate, one-sided system of 

 branchlets 70. Plagiosetum. 



