8 INTRODUCTION 
pair of species thus defined seems to have caused dis- 
quiet in the mind of Linnzus 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 Linnzan 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 Linnzan species, Dvaba 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 Linnzan 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. 
