GRASS FAMILY. 367 



3. THE PANICUM SUB-TRIBE. 



Spikclets 2-flowered, but the lower floret always imperfect, either 

 staminate or neutral ; in the latter case reduced to a single empty 

 palea (placed next to the lower glume if that be present) ; the upper 

 (terminal) flower (placed next the upper glume) only fertile. Flow- 

 ers polygamous or monoecious, sometimes apparently simple and 

 1-flowered from the abortion of the lower glume and the upper palea 

 of the neutral flower. Rarely both glumes are absent. 

 ^ 1. Palese of the fertile florets coriaceous or chartaceous, awnlcss, 

 not keeled, embracing the smooth grain, flattened parallel with the 

 herbaceous glumes. 



Spikelets appearing as if 1-flowered from the suppression of the 

 lower glume ; the single empty palea of the neutral flower oc- 

 cupying its place. Spikelets jointed with their short pedicels. 27. PASPALUM. 

 Spikelets manifestly 1 ) - 2-flowered (the lower floret neutral or 

 staminate) , the lower glume being present. 

 Spikelets not involucrate nor the peduncles bristle-bearing. 

 Lower glume small or minute. Sterile flower staminate 

 or neutral. 28. PANICUM. 



Spikelets spiked-panicled, the peduncles continued beyond 



the flower into a bristle. Otherwise as in 28. 29. SETARIA. 



Spikelets enclosed, 1 - 5 together in a hard and spiny bur- 

 like involucre. 30. CBNCHBUS. 

 ^2. Palese membranaceous or scarious, always of thinner and more 

 delicate texture than the (often indurated) glumes, frequently 

 awned at the apex. Spikelets usually in pairs or threes, panicled 

 or spiked ; monoecious or polygamous. 



Spikelets monoecious ; the pistillate ones imbedded in the rachis 

 of the continuous spike or in its separable joints. The stami- 

 nate spikelets above. 



Pistillate spikelets imbedded in the joints of the spontane- 

 ously separable naked rachis. 31. TRIPSACCM. 

 Pistillate spikelets along the sides of a continuous rachis, 

 which is enclosed by the sheaths of abortive leaves or 

 husks. 32. ZEA 

 Spikelets polygamous. Fertile spikelets with one perfect and one 

 sterile /staminate or mostly neutral) floret. Lower palea of the 

 perfect flower awned. 



Spikelets in pairs at each joint of the rachis, one pedicellate the 

 other sessile. 



The upper floret in each spikelet fertile. 33. SACCHARUM. 



The sessile spikelet only fertile. 34. ANDROPOGOX. 



Spikelets 2 -3 together, in loose open panicles, the lateral ones 

 sterile, or often mere rudiments. 36. SORGHUM. 



