266 CONTRIBUTIONS FEOM THE NATIONAL HERBARIUM. 



Inflorescence not a dense golden brown silky panicle ; pedicellate spike- 

 let stamlnate or rudimentary. 

 Pedicel of the sterile spikelet thickened, appressed to the thickened 

 rachis joint, or adnate to it. 

 Sessile spikelets sunken in cavities of the thickened rachis, the 

 first glume covering the opening ; sterile spikelet obscure. 



8, Manisuris (p. 275). 



Sessile spikelet not sunken in the rachis, the adnate rachis 



joint and pedicel sunken in the opening of the globose 



first glume; sterile spikelet large 9. Rytilix (p. 276). 



Pedicel of the sterile spikelet distinct, this and the rachis joint 

 usually slender. 

 Spikelets in reduced racemes of 1 to 5 (rarely 7) joints, these 

 peduncled in open panicles ; awns, if present, commonly 

 deciduous. 



Pedicellate spikelets staminate 15. Holcus (p. 286). 



Pedicellate spikelets wanting, the pedicel only present. 



16. Sorghastrum (p. 286). 

 Spikelets in evident racemes of several to many joints. 



Blades cordate, thin ; pedicellate spikelets obsolete or pres- 

 ent only in the lower part of the delicate subdigitate 



racemes 11. Arthraxon (p. 277). 



Blades linear, not cordate ; pedicellate spikelets present, at 

 least as rudiments. 

 Inflorescence an elongate panicle of whorled long- 

 peduncled slender glabrous racemes ; spikelets rauri- 



cate, awnless 14. Anatherum (p. 285). 



Inflorescence not a panicle of long-peduncled racemes ; 

 spikelets not muricate ; racemes commonly conspicu- 

 ously woolly. 

 Racemes 2, forking from the summit of the slender 

 peduncle, a staminate awnless spikelet borne in 



the fork 13. Cymbopogon (p. 284). 



Racemes 1 to many, not forking with a spikelet borne 

 in the fork 12. Andropogon (p. 277). 



3. NAZIEAE. 



Spikelets solitary, finally reflexed ; glumes subulate, awnless. 



22. Leptothrium (p. 289). 

 Spikelets 2 or more in a cluster, falling together. 



Glumes smooth, connate at base, forming a pitcher-shaped false involucre. 



20. Anthephoia (p. 288). 

 Glumes covered with hooked spines, forming little burs, not connate. 



21. Nazia (p. 289). 



4. MELINIDEAE. 



Spikelets awnless; inflorescence an attenuate panicle 24. Triscenia (p. 290). 



Spikelets awned ; inflorescence a many-flowered panicle. 

 Glumes awnless, the lemma with a bent or twisted awn. 



23. Arundinella (p. 289). 

 Glumes awned, the awns straight; lemma awnless 25. Achlaena (p. 290). 



