HOW TO KNOW THE GRASSES 



4a. Low, creeping perennial plants, rooting at 

 the nodes; staminate and pistillate spike- 

 lets on separate plants. Fig. 24 



See Fig. 247 (Buchloe dactyloides) 



Figure 24 



4b. Erect, coarse grasses; staminate spikelets at the 

 tip of the inflorescence; bony pistillate portion 



at the base. Fig. 25 



TRIBE XIII, TRIPSACEAE, page 184 



Figure 25 



5a. Spines of the burs hooked at the tips. . . 

 see Fig. 244. 



(Tragus berteronianus) 



5b. Spines of the burs straight, not hooked 



see Fig. 282. (Cenchrus pauciflorus) 



6a. Spikelets falling from the plants in clusters of 2 — many, never 

 singly 19 



6b. Spikelets either falling singly or breaking up into florets and leav- 

 ing the glumes behind on the plant 7 



7a. Spikelets of two unlike kinds (one staminate and the other pistil- 

 late) in the same or different inflorescences 8 



7b. Spikelets alike and nearly always with perfect flowers, or some- 

 times perfect and staminate or rudimentary ones borne to- 

 gether 12 



16 



