SS Mutability and Individual Variation. 



so far it is not within his power to call into existence new 

 characters. We all know that it is said to be impossible 

 to produce a blue Dahlia, a bright yellow Hyacinth and 

 so forth. To give our large flowered Canna white flow- 

 ers we must wait for the discovery of a new white flow- 

 ered wild species and then cross it with it (Crozy) ; in the 

 same way that our Gladioli have been made hardy and 

 the flowers of our Begonias large by crossing them with 

 newly discovered species which possess the character in 

 question. As soon as we arrive at an experimental phys- 

 iology of the origin of species, we expect to obtain con- 

 trol over much that at present seems beyond our reach. 



But let us return to the facts. Whilst w^e may hope 

 that the origin of new elementary species will one day 

 become the subject of direct investigation, we must be 

 perfectly clear as to the essential difference between these 

 and the so-called Linnean species which are (usually) 

 groups of elementary species. An elementary species 

 can be identified in anv e^iven case bv the test of culti- 

 vation ; how many such forms should be united to one 

 Linnean species is a matter for so-called taxonomic in- 

 stinct, just as is the settlement of the limits of genera 

 and families. 



Let us return to the rolling polyhedron and look at 

 the track it has left behind. Each piece of it, formed by 

 one side, represents an elementary species, and we will 

 imagine that all such species of a certain strip of the path 

 have left living offspring. The question is where to 

 place the boundaries of a "species" in such a group. 



Instead of a discussion I shall give the answer which 

 one of the most famous of the older systematists. Hooker, 

 has given in certain definite cases. First in regard to 

 Oxalis corniculata. The forms of this collective species, 



