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THE AMERICAN NATURALIST 



[ Vol. L 



demonstrated that the infertility of hybrids is due to the 

 abnormal development of the gametic elements, partic- 

 ularly the pollen grains, and have shown that whenever 

 the purity of a species is unquestionable, the spores are 

 uniform, in both size and shape, while, conversely, the 

 spores of hybrids are usually irregular, some appearing 

 normal and others being shrunken and devoid of proto- 



plasm. During the past year the writer has extended 

 these investigations to include a considerable number of 

 English species. Many interesting cases have been en- 

 countered, which will be elucidated in detail on another 

 occasion, but the conditions in the genus Epilobium are 

 so diagrammatic and typical, that it seems advisable to 

 describe them now. 



This genus is divided into two sections, Chamcenerion 

 and Epilobium proper, the chief differences being that in 

 the former the flowers are irregular and the spores not in 

 tetrads, while in the latter the flowers are regular and 

 the spores are persistent as tetrads. Both in eastern 



