574 GRAMINE.&. (GRASS FAMILY.) 



G. AMPHICARPUM. Glumes 3. Spikelets of 2 kinds, one in a terminal panicle, the other 

 larger, on a solitary subterranean peduncle. 



7. PANICUM. Glumes 4, the lowest smaller, the third staminate or neutral. 



* * Spikelets subtended by a bristly or spiny involucre. 



8. SETARIA. Involucre of 1 - several bristles persistent on the pedicel. 



9. CENCHRUS. Involucre bur-like, of several barbed spines partly united, and enclosing 



1-3 spikelets. 



10. PENNISETUM. Spikelets enclosed in an involucre of fine often plumose bristles. 



* * * Spikelets sunk in excavations of the thick rachis. 



11. STENOTAPHRUM. Culms creeping. Flowering branches short and erect. 



TRIBE II. ORYZE^E. Spikelets perfect or unisexual, 1-flowered. Empty glumes 

 none (except No. 1C). Stamens mostly 6 or more. 



* Spikelets perfect. 



12. LEERSIA. Spikelets compressed, mostly ciliate. Stamens 1-6. 



* * Spikelets unisexual. 



13. LUZIOLA. Staminate and pistillate spikelets in separate panicles. Stamens 6 - 11. 



14. HYDROCHLOA. Spikelets in simple few-flowered axillary and terminal spikes. Sta- 



mens G. 



15. ZIZANIA. Staminate and pistillate spikelets in the same panicle. Stamens 6. 



16. PHARUS. Spikelets in pairs, unequal, the smaller hexandrous, the larger pistillate. 



TRIBE III. MAYDE^E. Spikelets unisexual, the pistillate in excavations of the rachis 

 of the jointed spike. 



17. ROTTBtELLIA. A pistillate and staminate spikelet at the base of each joint of the 



spike. 



18. MANISURIS. A pistillate spikelet at the base, and a neutral one at the top of each 



joint of the spike. 



19. TRIPSACUM. Spikes pistillate at the base, staminate above. 



TRIBE IV. ANDKOPOGONE^E. Spikelets in pairs or threes on each joint of the 

 rachis of the spike or branch of the panicle, one sessile and perfect, the others pedi- 

 celled, stamiuate or neutral (rarely perfect). Glumes 4, the two lower larger, empty, 

 and more rigid, the third staminate or neutral, the floret hyaline and mostly awiied. 



* Spikelets in short-jointed spikes. 



20. ELIONURUS. Spikes single, long-peduncled. Spikelets awnless. 



21. ANDROPOGON. Spikes single, digitate, or panicled, mostly white-hairy. Spikelets 



awned. Lowest glume 2-keeled on the back. 



22. HETEROPOGON. Spikes clustered, 1-sided. Sterile spikelet 3-androus, its glumes 



flat, twisted. Floret long-awned. 



* * Spikelets panicled. 



23. IMPERATA. Sessile and pedicelled spikelets both perfect and awnless. 



24. ERIANTHUS. Sessile and pedicelled spikelets both perfect and awned, with an invo- 



lucral tuft at the base. 



25. SORGHUM. Spikelets in pairs or threes, only the sessile one perfect and awned. 



SERIES II. POACE^. Pedicel jointed above the lowest glume. 



TRIBE V. PHAL,ARIDE;E. Glumes 5, only the uppermost fertile, the two lower 

 empty, the middle ones staminate, neutral, or rudimentary. 



2G. PHALARIS. Middle glumes rudimentary. Floret triandrous. 



27. ANTHOXANTHUM. Middle glumes empty, awned. Floret diandrous. 



28. HIEROCHLOE. Middle glumes triandrous. Floret diandroue. 



