46 GRAMIXE.E. 



spongy rachis, grain exposed. 23. Zea. 



Female spikelets sunk in alternate cucullate 



dilatation of the racliis of the spike, which 



is hidden in the leaf-sheath ; grain not exposed. 



24. Euclilccmt. 



Sultribe II. Dimerieaz. Spikelets homogamous, secnnd on 

 a slender inarticulate rachis, 1-fld., diandrous. 



25. Dimeria. 



Subtribe III. Saccharcce. Spikelets homogamous, in com- 

 pound racemes or panicles (except Pottinia); gl. I. not 

 sunk in a hollow of the rhachis. 



* Ehachis not or rarely fragile. 



Spikelets in a cylindrical silvery thyrsus, 1-fld., 

 not awned. 26. Imperata. 



Spikelets panicled, 2-natc, 1-fld., awned. 



27 . Mi sea nth us. 

 ** Rhachis fragile. 



Spikelets in panicled racemes, 2-fld., awned. 



28. Spodiopogon. 



Spikelets in geminate digitate or fascicled spikes. 

 Spikelets binate, one sessile, the other pedicel- 

 led. 29. Pollinia. 

 Spikelets binate, both pedicelled. 



30. Polliniopsis. 



Spikelets in a thyrsus of spiciforui racemes, 1-fld., 

 awnless. 31. Sacckarum. 



Spikelets in a thyrsus of spiciform racemes, 1-fld., 

 awned. 32. Eriantlms. 



Subtribe IV. Isckcemece. Spikelets many, in solitary digi- 

 tate or fascicled spikes, usually heteromorphous ; gl. 

 I not sunk in a hollow of the rachis (see Pollinia in 

 SaccJiarece). 



* Margins of gl. I of sessile spikelets inflexed. 



