64 HEREDITARY CHARACTERS 



of finding out whether a difference belongs to the one or the 

 other category, is by a process of experimental breeding. If 

 the new character remains permanent, it is a mutation ; if it 

 disappears, it is a fluctuating variation. 



The particular case upon which de Vries first built his 

 hypothesis was that of (Enothera lamarckiana the evening 

 primrose. The European history of this species is obscure. 

 Some species of (Enothera was probably introduced from 

 America into France in the eighteenth century. Apparently 

 it does not exist in a wild state in America, but several 

 closely allied species do. De Vries, having searched in 

 vain in the neighbourhood of Amsterdam for a plant in 

 which large and permanent variations occurred, found (E. 

 lamarckiana in a deserted potato-field, whither it had pro- 

 bably escaped from some garden. On breeding these plants 

 he found that several large variations occurred, two of which 

 he called (E. brevistylis and (E. Icevifolia. He found that 

 they bred true when self-fertilised. He was also able in later 

 generations to establish several other new varieties which 

 apparently bred true. These he regarded as mutations, and 

 considered that (E. lamarckiana was passing through a stage 

 when it produced a large number of mutations which were 

 likely, if favourable, to produce new species ; if unfavourable, 

 to die out. 



There are several other cases which seem to show that 

 among domesticated plants under artificial conditions, these 

 large differences, sports, or mutations, may be perpetuated, and 

 may produce a race with permanent new characters. A well- 

 known example of this is the Shirley poppy, which occurred 

 as a sport and now breeds true. 



When we come to inquire, however, in more detail into 

 these mutations, we find that they become established as new 

 races only among plants that have been domesticated, that 

 is, which have been subjected to artificial selection. There 

 is no evidence at all that (E. lamarckiana is a wild species, 

 and there is a strong suggestion that it is artificially produced 

 by a cross. G. A. Boulanger's experiments, which gave very 



