24 MINNESOTA BOTANICAL STUDIES. 



Where the average number in a plot is between 5 and 15, the 

 species is called subcopious." A glance at the list given above 

 will show that these are often very striking components of the 

 prairie formations. Finally, in case the average is below 5 and 

 above .01, or one individual in ten plots, the species is called 

 "sparse." Gregario-copious species may be treated in the 

 same way, giving gregario-copious,^ etc. Antennaria cam^es- 

 tris in the prairie grass formations of the prairie region, aver- 

 aging 12 patches and 145 individuals per plot, would be gre- 

 gario-copious.^ 



Although this method involves no little labor, especially when 

 applied to social species, as we have been able to do success- 

 fully in some cases, such as the Peppergrass in the Pepper- 

 grass-Cactus formation, it has furnished results which amply 

 reward the time and work required. By means of such enum- 

 erations we have been able to determine many questions with 

 certainty which could only be guessed at otherwise, and we 

 have been able to make more accurate limitations of the regions 

 and particularly the transition areas than we had thought pos- 

 sible. 



