140 THE THEORY OF MUTATION 



* He (man) often begins his selection by some half- 

 monstrous form, or at least by some modification pro- 

 minent enough to catch the eye or to be plainly useful 

 to him.' But he goes on : ' Under Nature, the slightest 

 differences of structure or constitution may well turn 

 the nicely-balanced scale in the struggle for life, and 

 so be preserved.' * 



Of the origin of a new type of plant in this definite 

 and sudden fashion, the Shirley poppies afford an 

 excellent example. These originated in a mutation 

 of the common wild field-poppy (Pap aver rhceas). In 

 1880 the Rev. W. Wilks, Vicar of Shirley, near Croydon, 

 noticed among a patch of this plant growing in a waste 

 corner of his garden a solitary flower, the petals of 

 which showed a very narrow border of white. The 

 seeds which this flower produced were sown, and next 

 year, out of about two hundred plants, there were four 

 or five upon which all the flowers showed the same 

 modification. From these, by further horticultural 

 processes, the strain of Shirley poppies originated. 

 We may point out in passing that if the original plant 

 had been self-pollinated, a much larger proportion of 

 the new type might have been expected to appear in 

 the next generation. 



In the course of his own experiments, de Vries has 

 obtained quite a number of new types of plants by 

 methods like the above. It is to be observed that the 

 novelty hi these cases usually shows a considerable 

 range of normal variability of its own, and that its 

 first appearance is generally in the form of an extreme 

 * ' Origin of Species,' 6th ed., p. 60. 



