22 MIXNESOTA BOTANICAL STUDIES. 



of Andropogon scoparms occurred in the plot. The locality 

 was about six miles northwest of the preceding. 



Ainorpha canesce?is . . . . . . 192 



Ktihnistera occidentalis ( ?) . . , . .26 



Solidago rupestris . . . . . . 18 



Artejnisia g7iaphalodes . . . . . .17 



Solidago 7noUis ....... 12 



Solidago rigida ....... 3 



Helia^ttJuis 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 Schedomiardtis -paniculatus ^ represented by two 

 small patches. 



Platitago Purshii ....... 42 



Solidago jnollis ........ 23 



Lygodesniia juncea ...... 5 



Lepachys columnaris (dwarf) ..... 3 



Eriocarptan spintilosutyi ...... 2 



Grindelia sg7/arrosa ....... i 



JCuhnia ghitinosa ....... i 



L,esquerella 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 

 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- 



