454 



THE AMEBIC AN NATURALIST [VouXLTX 



years, "and was of about average uniformity and fer- 

 tility." 



Nothing could, it seems to me, emphasize more emphat- 

 ically the need of a scientific criterion for substratum homo- 

 geneity than the facts that correlations between the yields 

 of adjacent plots ranging from r = .115 to r = .609 can be 

 deduced from the data of fields which have passed the 

 trained eyes of agricultural experimenters as satisfac- 

 torily uniform. 



