ANDROPOGONEJE 



169 



callus, the whole much resembling the awned fruit of 

 Stipa spartea. 



208. Andropogon L. Sessile spike- 

 lets all alike in more or less elongated 

 racemes. The racemes may be single or 

 in pairs, or rarely 3 or 4 from a sheath- 

 ing bract, or they may be in naked 

 panicles. The species are usually coarse 

 perennials that inhabit prairies, hills, 

 pine-barrens and other dry places. Some 

 species are important native forage 

 grasses. Two of these are common on 

 the prairies of the Mississippi Valley, 

 the little bluestem (A. scoparius Michx.) 

 and the big bluestem (A.furcatus Muhl.) 

 (Fig. 16). The first species has solitary 

 racemes from each bract or spathe, and 

 is a representative of the subgenus 

 Schizachyrium. The other has 3 or 4 

 racemes in a naked digitate cluster. A 

 common but less valuable species, the 

 broom-sedge (A. virginicus L.), is found 

 in the Atlantic states on sterile soil. 

 This large genus of hundreds of species 

 is spread over the warmer regions of 

 both hemispheres. 



209. Cymbopogon Spreng. This 

 genus resembles Andropogon in having 

 racemes in pairs from sheathing bracts, 



but differs in that 1 or 2 of the lower- FIG. 16. Andropo- 



., , , ,. , , -,f gon furcatus. Inflores- 



most pairs of spikelets of at least 1 of cence, xy 2 . A joint 



. , . J . . _ . , of the rachis with a 



the racemes, are both stammate. In the fertile spikeiet below 



., and a staminate 



economic species the pairs ot racemes spikeiet above, x5. 



