38 Elementary Species 



tliey attempted to discredit it. Milde and many 

 others have opposed these new ideas with some 

 temporary success. Only of late has the school 

 of Jordan received due recognition, after 

 Thuret, de Bary, Rosen and others tested 

 its practices and openly pronounced for them. 

 Of late Wittrock of Sweden has joined them, 

 making extensive experimental studies concern- 

 ing the real units of some of the larger species 

 of his country. 



From the evidence given by these eminent 

 authorities, we may conclude that systematic 

 species, as they are accepted nowadays, are as 

 a rule compound groups. Sometimes they con- 

 sist of two or three, or a few elementary types, 

 but in other cases they comprise twenty, or fifty, 

 or even hundreds of constant and well differen- 

 tiated forms. 



The inner constitution of these groups is 

 however, not at all the same in all cases. This 

 will be seen by the description of some of the 

 more interesting of them. The European 

 heartsease, from which our garden-pansies have 

 been chiefly derived, will serve as an example. 

 The garden-pansies are a hybrid race, won by 

 crossing the Viola tricolor with the large flow- 

 ered and bright yellow V. lutea. They com- 

 bine, as everyone knows, in their wide range of 



