Effect of Cultivation 245 



others, de Vries 1 tried to show that garden-races have been produced 

 only from spontaneous types which occur in a wild state or from 

 sub-races, which the breeder has accidentally discovered but not 

 originated. In a small number of cases only has de Vries adduced 

 definite proof. On the other side we have the work of Korschinsky 2 

 which shows that whole series of garden-races have made their 

 appearance only after years of cultivation. In the majority of races 

 we are entirely ignorant of their origin. 



It is, however, a fact that if a plant is removed from natural 

 conditions into cultivation, a well-marked variation occurs. The 

 well-known plant-breeder, L. de Vilmorin 3 , speaking from his own 

 experience, states that a plant is induced to "affoler," that is to 

 exhibit all possible variations from which the breeder may make a 

 further selection only after cultivation for several generations. The 

 effect of cultivation was particularly striking in Veronica chamaedrys* 

 which, in spite of its wide distribution in nature, varies very little. 

 After a few years of cultivation this "good" and constant species 

 becomes highly variable. The specimens on which the experiments 

 were made were three modified inflorescence cuttings, the parent- 

 plants of which certainly exhibited no striking abnormalities. In a 

 short time many hitherto latent potentialities became apparent, so 

 that characters, never previously observed, or at least very rarely, 

 were exhibited, such as scattered leaf-arrangement, torsion, terminal 

 or branched inflorescences, the conversion of the inflorescence into 

 foliage-shoots, every conceivable alteration in the colour of flowers, 

 the assumption of a green colour by parts of the flowers, the 

 proliferation of flowers. 



All this points to some disturbance in the species resulting from 

 methods of cultivation. It has, however, not yet been possible to pro- 

 duce constant races with any one of these modified characters. But 

 variations appeared among the seedlings, some of which, e.g. yellow 

 variegation, were not inheritable, while others have proved constant. 

 This holds good, so far as we know at present, for a small rose-coloured 

 form which is to be reckoned as a mutation. Thus the prospect of 

 producing new races by cultivation appears to be full of promise. 



So long as the view is held that good nourishment, i.e. a plentiful 

 supply of water and salts, constitutes the essential characteristic of 

 garden-cultivation, we can hardly conceive that new mutations can 

 be thus produced. But perhaps the view here put forward in regard 

 to the production of form throws new light on this puzzling problem. 



1 Mutationstheorie, Vol. i. pp. 412 et seq. 



2 Korschinsky, " Heterogenesis und Evolution," Flora, 1901. 



3 L. de Vilmorin, Notices sur I 'amelioration des plantes, Paris, 1886, p. 36. 



4 Klebs, Kiinstliche Metamorphosen, Stuttgart, 1906, p. 152. 



