DESCRIPTIONS OF TRIBES AND GENERA. 45 



two-flowered tlie first empty glume has a 

 median longitudinal furrow. . 13. Pollinia. 

 II. Spikelets two-flowered, first empty glume 

 without a longitudinal furrow. 



25. Ischsemum (in part). 



y. Racemes in a mucli-branched panicle upon an 



elongated main axis, the lateral racemes sessile. 



I. Spikelets awned 12. Erianthus. 



II. Spikelets unawned. . . .11. Saccharum. 



6. Racemes (usually short) in branched panicles 



with elongated main axis, the lateral racemes 



pedicellate 14. Spodiopogon. 



B. Spikelets heterogamous or rarely homogamoits, the joints 

 of the axis of the raceme {false spike) appressed or grown 

 to the pedicels of the primary spikelets, forming together 

 ivith the pedicels a hollow or excavation for the reception 

 of the secondary spikelets ; fertile glumes alioays awnless. 

 {Rottboelliea\) 



a. Joints of the rachis and pedicels complanate, not 

 pressing against each other, but opposite ; the £ 

 spikelets sessile upon each joint of the axis and 

 their posterior sides pressed against each other, 

 embracing only by the edges. . 17. Ratzeburgia. 



b. Joints of rachis and pedicels thick, appressed or 

 grown together, the $ spikelets single upon each 

 joint (very rarely in twos), entirely enclosed in 

 front. 



a. First empty glume naked, awnless (at most 

 only the terminal spikelet caudate). 

 I. The first empty glume flat or simply con- 

 vex 18. Rottboellia. 



II. First empty glume globose, with an open- 

 ing upon the inner side which is closed by 

 the joint of the rachis. . . 19. Manisuris. 

 §. The first sterile glume of all or of only the 

 pedicelled spikelets awned or caudate. 

 I. Racemes simple or again disposed in 

 racemes (compound). 



1. Spikelets, both sessile and pedicellate 

 (the latter sometimes apparently re- 



