46 Elementary Species 



species exactly in the same way as the tricolored 

 field-pansies. 



Summarizing the general result of this de- 

 scription we see that the original species Viola 

 tricolor may be split up into larger and lesser 

 groups of separate forms. These last prove to 

 be constant in pedigree-cultures, and therefore 

 are to be considered as really existent units. 

 They are very numerous, comprising many 

 dozens in each of the two larger subdivisions. 



All systematic grouping of these forms, and 

 their combination into subspecies and species 

 rests on the comparative study of their charac- 

 ters. The result of such studies must neces- 

 sarily depend on principles which underlie 

 them. According to the choice of these 

 principles, the construction of the groups 

 will be found to be different. Wittrock trusts 

 in the first place to the morphological charac- 

 ters, and considers the development as passing 

 from the more simple to the more complex 

 types. On the other hand the geographic dis- 

 tribution may be considered as an indication of 

 the direction of evolution, the wide-spread 

 forms being regarded as the common parents of 

 the minor local species. 



However, such considerations are only of sec- 

 ondary importance. It must be borne in mind 

 that an ordinary systematic species may include 



