22 MINNESOTA BOTANICAL STUDIES. 



of Andropogon scopartus occurred in the plot. The locality 

 was about six miles northwest of the preceding. 



Amorpha canescens . . . . . . 192 



Kuhnistera occidentalis ( ?) . . . .26 



Solidago rupestris . . . . . . 1 8 



Artemisia gnaphalodes . . . . . .17 



Solidago mollis . . . . . . . 12 



Solidago rigida ....... 3 



Helianthus rigidus ...... 2 



The following count, made in the buffalo grass formation, 

 about two miles beyond the one last set forth, shows the latter 

 formation as affected by the near proximity of the prairie gras, 

 formation. The number of secondary species, small as it is, is 

 very large for that formation. Where this count was mades 

 the dominant grass was Bouteloua oltgostachya. The only 

 other grass was Schedonnardus -paniculatus , represented by two 

 small patches. 



Plantago Purshii ....... 42 



Solidago mollis . . . . . . . 23 



Lygodesmia juncea ....'.. 5 



Lepachys columnaris (dwarf) ..... 3 



Eriocarpum spinulosum ...... 2 



Grindelia squarrosa . . . . . I 



Kuhnia glutinosa ....... i 



Lesquerella argentea . . . . . . i 



The constant diminution in the number and abundance of 

 secondary species as one passes from the prairie grass formation 

 of the prairie region to the buffalo grass and bunch grass forma- 

 tions of the transition area and of the sand hill region is well 

 illustrated by these figures. The difference betweeen the 

 prairie grass formation in its ordinary situations and in the 

 transition area, and between the buffalo grass formation of the 

 "range" and the same formation in the transition area is better 



O 



shown by figures obtained from such enumerations than in any 

 other way. Many other examples of the efficacy of this method 

 in representing changes in the floral covering as one passes 

 from one district to another might be given. 



The method of actual enumeration of the individual plants 

 present in plots of a given size makes accurate limitation of the 

 several grades of abundance possible. Of course, this has noth- 



