316 



L. SpikeleU beterogamous or rarely homogamous, the joints 

 of the axis of the raceme (false spike) appressed or 

 grown to the pedicels of the primary spikelets, forming 

 ■ hollow or excavation for the reception of the secondary 

 spikelets ; fertile glumes always awnless. 



2. Spikelets 2-nate ; first empty glume flat (12) Rottliurllia 



2. Spikelets 2-nate: first empty glume globose (13) Mniii.iiiri.i 



2. Spikelets solitary; first empty glume convex (14) OpMvnu 



1. Spikelets heterogamous. the sessile hermaphrodite, rarely 

 pistillate, the pedicellate staminate, empty or wanting, 

 very rarely all hermaphrodite or all pedicellate ; joints 

 of the racemes not strongly thickened, nor with excava- 

 tions for the reception of the spikelets. 

 2. Sessile spikelets 2-flowered. 



:',. Racemes reduced to the terminal joint with 

 three spikelets, and enclosed by a sheath- 

 ing leaf or bract (17) Aplndn 



::. Racemes with many joints. 



4. Spikes rarely solitary ; spikelets 2- 



flowered, awned (15) Itohaemum 



4. Spikes solitary; spikelets 1-flowered, 



the first glume pectinate ( l(i) Kremochloa 



2. Sessile spikelets 1 -flowered. 



.",. A false whorl of four or more staminate or 

 empty spikelets at the base of each raceme ; 

 racemes usually subtended by a sheathing 



leaf (20) Themeda 



3. No distinct whorl of staminate or empty 

 spikelets at the base of the racemes, or 

 where an imperfect one occurs, the ra- 

 cemes in pairs, subtended by a leaf-sheath. 

 4. Fertile glume awned from the back 



or base; leaves cordate at the base.. (IS) Arlhriu'ou 

 4. Fertile glumes awned from the apex 

 or from a more or less dee]) cleft, 

 or awnless ; leaves not cordate at 

 the base (10) Andropogon 



Tribe III. ZOISIE^rE. 



1 . Spike slender; spikelets narrow; first and second glumes 



awned (21) Perotia 



1. Spike rigid; spikelets appressed to the rhachis, not awned.. (22) Zoitia 



Tribe [V. TRISTEGINEiE. 



I. Flowering glumes of the hermaphrodite flowers awned; 

 awns usually geniculate and twisted below ; slender 

 grasses (23) .1 run&inella 



I. Flowering glumes awnless; spikelets minute; very coarse 



grasses (24) Thj/aanolaena 



Tribe V. PANICE^l. 



l Spikelets all perfect. 



2. Spikelets without any special covering or involucre 

 consisting of spines or bristles. 



.'!. Empty glumes two ; perfect flower one in 

 each spikelet. 



4. Lower empty glume with a thickened 



ring-like callus (27) Eriochloa 



4. Lower empty glume without a ring- 

 like and thickened callus ; spikelets 

 in one-sided racemes or spikes. 

 !">. Spikelets ovate or orbicular, 



obtuse, rarely acute (2. r >) Paapalum 



5. Spikelets lanceolate, acute or 



acuminate (2ti) Digitaria 



