CHAPTER XVI 

 TBIBE II. ANDROPOGONE^J 



THIS great tribe is represented in the warmer regions 

 of both hemispheres but is absent from the arctic and 

 alpine regions and is poorly represented in the cooler 

 temperate regions. The spikelets are usually arranged in 

 pairs at each joint of a spike-like raceme, 1 sessile, the 

 other pedicelled. The rachis of the raceme is usually 

 articulated and breaks up at maturity into joints. The 

 racemes are often woolly with long hairs and may be 

 arranged in a compound inflorescence. Sometimes the 

 racemes are reduced to the terminal joint of 3 spikelets, 

 in which case the compound inflorescence is a panicle, 

 as in Johnson-grass. The spikelets nearly always consist 

 of 2 glumes, at least 1 of which is firm or indurated, a 

 sterile lemma, and a terminal fertile floret. The bracts 

 above the glumes are usually thin and hyaline. The fertile 

 lemma often bears a bent or twisted awn. Grasses of this 

 kind are commonly abundant on savannas and plains in 

 the tropics and in prairie regions of the United States, and 

 many species are useful forage grasses. There are about 

 50 genera in the tribe but only a few contain species of 

 interest to Americans. Of the 5 sub-tribes, only 2 will be 

 mentioned here. 



KEY TO THE GENERA OF ANDROPOGONE^E 



A. Axis of the spike glabrous, much thickened, 

 with excavations holding the spikelets; fertile 

 lemma awnless. 



(164) 



