15 



Tribe II.— ANDROPOGONE^E. 



Spikelets in spike-like racemes, two at each joint of the articulate 

 rachis, one sessile and hermaphrodite, one pedicellate, the latter 

 hermaphrodite, staminate, neuter, or reduced to the pedicel alone; 

 glumes usually four, the first and second empty, larger and much 

 firmer in texture than the others, the third usually empty, with a 

 staminate flower in its axil, very rarely awned, the fourth or flower- 

 ing glume hyaline, usually awned, awn usually twisted or geniculate. 



This tribe contains about four hundred species divided 

 among twent} T -nine genera, of which the genus Andro- 

 pogo?i, with one hundred and ninety species, is by far 

 the largest and probably the most important. Sugar- 

 cane belongs to this tribe in the genus Saccharum. 

 Our best-known representatives of the Andropogonea? 

 are the common broom sedge, Androjjogon virginicus, 

 and the big blue stem, Andropogon provincidlis. In 

 the same genus are now classed the man} 1 - varieties of 

 sorghum. The members of the tribe are distributed 

 throughout the tropical and warmer temperate regions 

 of both hemispheres. 



KEY TO THE GENERA OF THE ANDROPOGONEA. 



1. Axis of the spikes or racemes hairy; fertile glumes usually 

 awned 2 



1. Axis of the spikes or racemes naked; fertile glumes awnless. . 6 



2. Spikelets all alike (homogamous) : 3 



2. Spikelets not all alike (heterogamous) 7 



3. Floral axis continuous 4 



3. Floral axis articulated 5 



4. Panicles dense; spikelets awnless 5. Imperata 



4. Panicles somewhat fan-shaped; spikelets awned. 6. Miscanthus 



5. Spikelets awned 8. Erianthus 



5. Spikelets awnless 7. Saccharum 



6. First empty glume of the hermaphrodite spikelet flattened or 



somewhat convex 9. Manisuris 



6. First empty glume of the hermaphrodite spikelet hard and glob- 



ular, pitted externally 10. Hackelochloa 



7. Rachis imperfectly articulated; primary spikelet on a short 



pedicel, awnless; secondary spikelet pedicellate and long 

 awned 11. Trachypogon 



7. Rachis distinctly articulate; secondary spikelet sessile 8 



8. Spikelets awnless 12. Elionurus 



8. Spikelets awned 13. Andropogon 



