45 



which it was impossible to increase the size of the g-rains. 

 By this process of selection the investigator had probably 

 succeeded in isolating a pure strain of the particular 

 variety with which he was experimenting, characterised bv 

 a larger seed than the sample with which he started, which 

 was, no doubt, a mixture of races, some producing smaller 

 and some larger seeds. But once a pure line had been 

 obtained, though it showed slight fluctuations, yet it could 

 not be improved by selection of die extremes of these 

 fluctuating variations. 



We know, however, of other variations which arise from 

 time to time in all species of plants, and which are very 

 different from the fluctuations as wx may term those 

 described above. Sometimes we come across new^ forms 

 which differ considerably from, the normal type in one or 

 more characters, as, for example, the cut-leaved varieties of 

 so many plants. In this case we do not iind a series of 

 forms intermediate between the cut-leaved individual and 

 those with normal foliage. This second type of variation 

 which arises suddenly Darwin called a sport, and he con- 

 sidered it to be of comparatively little importance in the 

 evolution of plants, as its very infrequent occurrence would 

 cause it to disappear m nature by constant inter-crossing 

 with the more numerous normal forms. By artificial selec- 

 tion, however, man can perpetuate and establish these 

 sports, as has obviously been the case with many of those 

 forms which took the fancy of the horticu'lturist. It is to this 

 kind of variation that w^e owe so many of our interesting 

 and peculiar forms of cultivated plants. Recently a Dutch 

 botanist, De Vries, has endeavoured to show that this 

 second kind of variation, which he calls viutaiiun, to dis- 

 tinguish it from the former or fluctuating variation, is of 

 more frequent occurrence than had been supposed by 

 Darwin. He observed that a certain large group of plants 

 of Evening Primrose which had established itself in a wild 

 condition in Holland showed a very considerable amount 

 of mutation, and his expeiiments and other observations 

 led him to the conclusion that at certain periods, possibly 

 owing to changed environment, plants passed into a phase 

 of mutation, during which numerous new sub-species or 

 races might arise. Interesting and important as JDe Vries' 

 experiments are, his case cannot be considered proved until 

 we know more about the previous history of the plants 

 which show^ such considerable mutation. At present we do 



