1Rbo6oia 



JOURNAL OF 



THE NEW ENGLAND BOTANICAL CLUB 



Vol. 6 November, 1904 No. 71 



HYBRIDISM IN THE GENUS VIOLA. 



Ezra Brainerd. 



(Plate 58.) 



At the close of my " Notes on New England Violets" in Rhodora, 

 vi. 17, I ventured to suggest that the newly recognized species of blue 

 stemless violets occasionally produced hybrids. Another season of 

 diligent study of this problem, both in the field and in herbaria, has 

 brought to light numerous facts that confirm this theory. Indeed 

 the evidence, when taken in all its detail, seems to place the conclu- 

 sion beyond any reasonable doubt. The object of the present paper 

 is to report some of these facts and to present the evidence. 



There is a widespread reluctance on the part of American botanists 

 to regard an intergrading form as a result of natural hybridism. 

 The systematists of the Old World have far less prejudice, perhaps 

 because they have studied for a longer time and with more care and 

 thoroughness the behavior of their species in the field. The burden 

 of proof is, of course, on the advocates of the supposed hybrid ; but 

 that proof should be considered with candor, and not thrust aside from 

 a preconception that hybridism is most improbable. For if hybrids 

 ever occur in a state of nature, and few will deny it altogether, we 

 should expect them to occur among the twelve or fifteen segregates of 

 the old Viola cucullata-sagittata group. These segregates are so 

 closely allied, that Dr. Gray, who was acquainted with most of the 

 extreme types, recognized only two polymorphous species with inter- 

 gradient forms, and that even to-day after prolonged study experts are 

 widely apart as to the delimitation of species. The fioral structure 

 indicates that the petaliferous fiowers are incapable of self-fertiliza- 



