Pool: THE VEGETATION OF THE SANDHILLS OF NEBRASKA 261 



when the water-content of the surface soil is being rapidly dimin- 

 ished. The same species is sparsely scattered over the hills but 

 nowhere does it assume the importance that typifies its habit in this 

 association. 



Veronica perigrina, frequently developed in great abundance, 



Fig. 16. Buffalo grass, Bulhilis dactyloides. Pistillate plant, a; 

 staminate plant, b; pistillate spike, c; staminate 

 spikelets, d. (From Shantz.) 



is an earlier vernal occupant of the same areas that are later con- 

 trolled by the Festuca. 



So also Plantago piirshii and Lepideum apetalum are often 

 seen scattered through the association at the time the fescue grass 

 is at its height. The patches of Plantago are especially noticeable 



