317 



3. Empty glumes two ; perfect flowers two in 



each spikelet (28) Isachite 



3. Empty glumes three ; perfect flower one in 

 each spikelet. 



4. Glumes unawued ; spikelets paniclecl 



or spicate (29) Pniiiciiiii 



4. Glumes unawned ; spikelets of Pani- 

 cuin, but the flowering glume nar- 

 rowed into a short stipe or with two 



appendages or pits at the base (30) Ichimnthns 



4. Empty glumes or flowering glumes 

 awned or awn-pointed. 



5. Flowering glumes unawned ; 

 empty glumes awned or awn- 

 pointed. 



6. Prostrate or ascending 

 grasses ; racemes or 

 clusters of few spike- 

 lets ; empty glumes 

 glabrous or pubescent.. (31) Oplismcnus 

 6. Erect grasses ; racemes 

 of many spikelets ; 

 empty glumes often 



muricate-hispid (29) PanicHni ^ Echiiinrliloa 



5. Flowering glume awned ; nerves 



of the second empty glume 



broadly fimbriate ; palea of 



the third glume deeply cleft.. (33) Axonopn.i 



2. Spikelets subtended by an involucre, consisting of 



from one to many bristles or spines which are 



sometimes grown together. 



3. Involucre of two spine-bearing valves (34) Cenchrus 



3. Involucre of numerous bristles. 



4. Spikelets fasciculate ; involucral bris- 

 tles falling with the spikelet (35) Pennisettim 



4. Spikelets usually solitary ; involucral 

 bristles persistent after the fall of 



the spikelet (32) Setaria 



3. Involucre of solitary bristles. 



4. Inflorescence in open panicles ; pros- 

 trate aquatic grasses (35) Chcunaeraphis 



4. Inflorescence in dense cylindrical 

 spikes or spike-like panicles ; erect 



grasses (32) Sclaria 



1. Spikelets monoecious or dioecious. 



2. Monoecious ; slender prostrate grasses ; inflores- 

 cence a terminal spike, the two lower spikelets 

 perfect, the four to six upper ones staminate.. (37) Thnarca 

 2. Dioecious ; very coarse prostrate grasses ; pistillate 

 flowers collected into large globose heads with 

 very long spines ; staminate flowers in umbel- 

 lately disposed racemes (38) Spinifcx 



Tribe VI. ORYZE^. 



1. Spikelets unisexual ; fruiting glumes inflated; leaves broad.. (39) Lcptaspis 

 1. Spikelets perfect; fruiting glumes not inflated. 



2. Empty glumes two, short but distinct ; spikelets 



awned or awnless (40) Oryza 



2. Empty glumes wanting; spikelets awnless {il) Lecrsia 



Tribe VII. PHALARIDE^. 



1. First and second glumes minute, the third and fourth longer 



than the flowering glume (42) Micrnlaena 



1. First and second empty glumes equaling or exceeding the 



third and fourth (43) Aiithoxanthum 



