I From the Bulletin OF the Torrby Botanical Club, 42: 463-479. 23 S 1915.] 



Notes on Rosaceae — X 



p. A. Rydberg 



RuBUs Hybrids 

 Hybrids are rather common in the genus Rubus, especially 

 among the blackberries. Numerous hybrids have been admitted 

 in Europe. The only really good attempt made to segregate 

 hybrid forms in America, was that by Mr. Bicknell.* Mr. Bicknell 

 studied these forms in the field and in most cases found the 

 supposed parents growing in the immediate vicinity. I also have 

 studied blackberry hybrids two summers in the Adirondacks, the 

 Catskills, the mountains of southwestern Virginia, western North 

 Carolina, and eastern Tennessee, and around Ottawa, Canada. 

 It is a pity that it never occurred to Mr. Blanchard, who did so 

 much valuable work on the blackberries, to explain the numerous 

 forms as, partly at least, due to hybridity. It would not have 

 been very hard to determine whether or not many of his new species 

 probably had arisen through hybridizing. Mr. Bicknell, without 

 having seen many of Mr. Blanchard's species in the field, reduced 

 nearly all of them into hybrids or into synonyms of older species. 

 I think that his interpretation was correct in the majority of 

 cases, but that he went too far in his reduction in some others. It 

 is risky to make pronunciations without seeing the species in the 

 field, and my course in the North American Flora was perhaps not 

 so wise. It may have been better to leave many of the supposed 

 species as such than to pronounce them as hybrids, without any 

 better proofs than the finding of intermediate and intergrading 

 characters. No definite conclusion can be had, however, with- 

 out experimental work in crossing. The only alternative course to 

 pursue would have been to admit all the proposed species as such 

 and to describe twice as many more, most of them without any 

 definite distinctive characters. In such a case, a key would have 

 been impossible to make. 



* Bull. Torrey Club 38: 103-133. 1911. 



463 



