8 INTRODUCTION 



pair of species thus defined seems to have caused dis- 

 quiet in the mind of Linnaeus himself, and he recom- 

 mended his disciples to have no dealings with these 

 inferior varieties, as being beneath the dignity of a 

 botanist to notice. Of late years these minor species 

 have excited much attention, and it is to a study of 

 this kind of species in particular that the mutation 

 theory of de Vries owes its origin, as will be told in a 

 later chapter. 



Such minor groups, occurring within the limits of a 

 single Linnaean species, and subdividing it into smaller 

 collections of individuals, were made the object of 

 special study in the case of plants by the French 

 botanist, Jordan ; and for this reason they are some- 

 times referred to as Jordan's species. Jordan, for 

 example though the example is indeed an extreme 

 one described more than two hundred different types, 

 all of which would formerly have been included in 

 the single Linnaean species, Draba verna. To take a 

 more familiar instance. We find in the ' British 

 Flora ' of Bentham and Hooker the primrose, the 

 cowslip, and the true oxlip, all described as varieties 

 of one and the same species ; yet these three kinds of 

 plants are now almost universally recognised to be 

 as good species as any in nature.* In a similar way, 

 on closer investigation, it has been found necessary to 

 split up a considerable number of Linnaean species } 

 and to subdivide each into several species of smaller 

 range. 



* A contrary opinion is, however, expressed in the Journal 

 of Botany for July, 1906. 



