THE ORIGIN OF NEW FORMS 



191 



over, to accept his statement to the effect that his work is "in 

 full accord with the principles laid down by Darwin." The latter 

 held that new^ forms arise regularly from indefinite variations; 

 De Vries derives them from mutations; Darwin regarded natural 

 selection as a necessary agent in originating new forms by varia- 

 tion, while to De Vries it is merely a process that acts after origin 

 is complete. 



206. Fundamental methods of evolution. From the foregoing 

 it is evident that new forms probably originate in one of three 



Fig. QQ.Solulago oreophila and its alpino form, Solidngn dccumbcii^^. 1 he 



latter is due to dwarfing, arising from low temperature and from tlie 



increased water loss caused by decreased pressure at high altitudes. 



different ways, i.e., by indefinite variability or variation, by 

 definite variation or adaptation, or by mutatitm. New forms 

 arise also by crossing or hybridization, which has usually not 

 been accounted a method of evolution. It is interesting to note 



