Mutations 79 



Frequency of occurrence of mutations. In general, it 

 may be said that the occurrence of mutations is rare. 1 



In order to obtain a clear understanding of this subject, 

 it may be divided into four sections : 



1. Spontaneous occurrence of new varieties in the wild 

 state. 



2. Spontaneous occurrence of new species in the wild 

 state. 



3. Spontaneous occurrence of new varieties under 

 cultivation. 



4. Spontaneous occurrence of new species under 

 cultivation. 



The term "variety" as here used carries the meaning 

 given by de Vries, that of a group of plants differing 

 from others in one systematic character. 



Spontaneous occurrence of new varieties in the wild 

 state. 2 New varieties of plants are seen to occur rather 

 rarely in the wild state. This may be due to two causes : 

 (1) A lack of critical examination of wild plants for such 

 spontaneous mutation; and (2) if these mutations do 

 occur, they are likely to meet premature death because 

 of the severe competition to which all wild forms are 

 subjected. 



As our wild plants are being studied more critically, 

 it is being found that they do produce a much larger 

 number of new varieties than was formerly supposed. 



In the case of the peloric toad-flax, which has been 

 studied carefully by de Vries, the mutations are so numer- 



1 De Vries, p. 191. 



2 De Vries, " Species and Varieties, their Origin by Mutation," 

 chapter on the Origin of Wild Species and Varieties, p. 576. 



