414 POACE^. 



northern Mexico. Often called " Grama-grass," and some of them 

 called " Bntfalo-grass." 



The following division into tribes shows the variation of this 

 genus very well. 



A. Cliondrosium Desv. as a genus. Spikes one to several, 

 linear or obIo?ig, more or less falcate, the usually very 

 numerous spikelets pedinatehj crowded on one side of the 

 racliis; terminal empty glumes usiudhj 3-aicned. . . .(a) 



a. Spike always solitary (b) 



b. Empty glumes glabrous.* (c) 



c. Floral glume 2.5-3 mm. long 1 



c. Floral glume 5-6 mm. long 2 



b. Empty glumes villous. Plant 20-40 cm. high ; empty 



glumes 2-3 mm. long 3 



a. Spikes usually 2 or more (e) 



e. Spikes very dense, oblong, linear; empty glumes vil- 

 lous (f) 



f . Rachilla above fertile floret glabrous, spikes 2 cm. 



long 4 



f. Ivachilla above fertile floret bearded 5 



e. Spikes dense, narrowly linear ; empty glumes usually 



glabrous (h) 



h. Floral glume 1.5 mm. long 6 



h. Floral glume 2 mm. long, besides the teeth, 



hairy 7 



h. Floral glume 2.5-3 mm. long, spikes 1.5-2.5 cm. 



long B 



Ti. Floral glume 3 mm. long, spikes 2-3 cm. long. . 9 

 h. Floral glume about 3 mm. long; spikes 5-7 in 



number, 2.5-3 cm. long 10 



€. Spikes looser and more slender; lower glumes gla- 

 brous (i) 



i. Peduncles villous; floral glume 1-awned. . . 11 



* B. tenuis Griesb. in purt. A densely tufted perennial 20-40 cm. high. 

 This may be expected from Mexico. 



