626 Mutations 



means of the crossing of the offspring of a 

 single mutant with previously existing sorts, is 

 a very common feature in horticultural prac- 

 tice. It warns us that only a small part of the 

 novelties introduced yearly are due to real mu- 

 tations. Further instances of novelties with 

 such a common origin are the purple-leaved 

 dahlias, the gooseberries without prickles, the 

 double petunias, erect gloxinias and many 

 others. Accumulation of characters, acquired 

 in different races of a species, may easily be 

 effected in this way ; in fact it is one of the im- 

 portant factors in the breeding of horticultural 

 novelties. 



I have alluded more than once in this lecture 

 to the question whether it is probable that mu- 

 tations occur in one individual or in more. 

 The common belief among horticulturists is 

 that, as a rule, they appear in a single plant. 

 This belief is so widespread that whenever a 

 novelty is seen for the first time in two or more 

 specimens it is at once suggested that it might 

 have originated in a previous and overlooked 

 generation. Not caring to confess a lack of 

 close observation, the number of mutants in 

 such cases is usually kept secret. At least this 

 statement has been made to me by some of the 

 leading horticulturists at Erfurt, whom I visited 

 some years ago in order to learn as much as 



