186 CONTKIBUTIONS FKOM THE NATIONAL HERBARIUM. 



Staminate and pistillate spikelets in different inflorescences; pistillate spikelets 



inclosed in a bony bead-like involucre (Maydeae) '. 1. Coix (p. 190). 



Spikelets all perfect, or unisexual and arranged in pairs, the pistillate sessile, the 



staminate pedicellate (or all pedicellate in Trachypogon) . (Andropogoneae.) 



Joints of the rachis much thickened and excavated to receive the spikelets. 



First glume of the perfect spikelet flat or somewhat convex; perennials. 



6. Manisuris (p. 191). 

 First glume of the perfect spikelet hemispherical, pitted; annual. 



7. Hackelochloa {p. 191). 

 Joints of rachis not thickened nor excavated for the reception of the spikelets. 

 Spikelets all alike, perfect; inflorescence a plume-like panicle. 

 Axis of racemes continuous, not articulate; spikelets awnless. 



2. Imperata (p. 190). 

 Axis of racemes articulated. 



Spikelets awnless 3. Saccharum (p. 190). 



Spikelets awned 4. Erianthus (p. 190). 



Spikelets not alike. 



All pedicellate; the perfect long-pedicellate, long-awned, the stami- 

 nate short-pedicellate, awnless 8. Trachypogon (p. 191). 



Sessile and pedicellate, the former perfect, awned, the latter stami- 

 nate, empty or wanting. 



Perfect spikelets transversely rugose 5. Ischaemum (p. 191). 



Perfect spikelets not transversely rugose. 



Sessile spikelets not all alike, the first to fifth pairs homog- 

 amous; awns 10 cm. long, stout; glumes bearing oil glands, 



lemon-scented when fresh 13. ITeteropogon (p. 196). 



Sessile spikelets alike throughout. 



Racemes of several to many joints, at least some of the 



racemes sessile 9. Andropogon (p. 192). 



Racemes reduced to 1 or 2 joints, all the racemes more 

 or less pedunculate. 

 Pedicellate spikelets present, usually 2 to each 



sessile spikelet 10. Holcus (p. 195). 



Pedicellate spikelets wanting. 



Awns not over 2 cm. long, delicate. 



11. Sorghastrum (p. 195). 

 Awns over 10 cm. long, stout.' 



12. Rhaphis (p. 195). 

 Lemma and palea membranaceous or indurated ; sterile lemma when present like the 

 glumes in texture. 



Lemma and palea membranaceous; axis of inflorescence not breaking up at 

 maturity. 



Spikelets 3 to 5 together, the clusters arranged in spikes, the glumes indu- 

 rated. (ZOYSIEAE.) 



Glumes covered with hooked spines 14. Nazia (p. 196). 



Glumes not spiny, united into a somewhat pitcher-shaped pseudo- 

 involucre 15. Anthephora (p. 196). 



Spikelets distinct, paniculate. (Tristegineae.) 



Fertile lemma awned; rather robust grasses 16. Arundinella (p. 196). 



Fertile lemma awnless; low grass with tuft of involute rather wiry basal 



leaves [doubtfully placed in this tribe] 17. Triscenia (p. 198). 



Lemma and palea cartilaginous or chartaceous-indurated, conspicuously differ- 

 ent in texture from the membranaceous glumes, rarely but little indurated. 

 (Paniceae.) 



