520 Mutations 



measure as to give distinct indications. All have 

 to be given a trial in the garden under conditions 

 as similar as possible to their natural environ- 

 ments. Cultivated plants are of course to be 

 excluded. Practically they have already under- 

 gone the experience in question and can not be 

 expected to change their habits soon enough. 

 Moreover they are often of hybrid origin. The 

 best way is to experiment with the native plants 

 of one *s own country. 



I have made such experiments with some hun- 

 dred species that grow wild in Holland. Some 

 were very variable, as for instance, the jointed 

 charlock (Raphanus Raphanistrum) and the 

 narrow-leaved plantain (Plantago lanceolata). 

 Others seemed more uniform, but many species, 

 collected without showing any malformation, 

 subsequently produced them in my garden, 

 either on the introduced plants themselves or 

 among their offspring. From this initial ma- 

 terial I have procured a long series of heredi- 

 tary races, each with some peculiar anomaly for 

 its special character. But this result was only 

 a secondary gain, a meager consolation for the 

 negative fact that no real mutability could be 

 discovered. 



My plants were mostly annuals or biennials, 

 or such perennials as under adequate treatment 

 might produce flowers and seeds during their 



