EXPERIMENTAL EVOLUTION 



mutate. A plant that arises by mutation is an elementary 

 species, or mutant; and the theory that mutations (and not 

 fluctuations) explain the origin of the fittest, and supply 

 the materials upon which natural selection operates in the 



r\p 



Extre, 



1^^ Fluctuainiyarkiion^^^,.^-;^^^ 



Maan 



Fig. 56.^ — Diagram to illustrate the difference between fluctuating 

 variation and mutation; 0, original point of suspension; M, new point of 

 suspension after the mutation has occurred. 



formation of new species, de Vries called the mutation 

 theory. 



90. Examples of Mutation. — The kohlrabi, cauliflower, 

 and other horticultural varieties of the wild cliff-cabbage 

 (Fig. 57), are belie.ved to be mutants, and to have arisen, 



