CHAPTER XVI 
Trise II. ANDROPOGONE 
TuHIs 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 
A. Axis of the spike glabrous, much thickened, 
with excavations holding the spikelets; fertile 
lemma awnless. 
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