EVERSPORTING VARIETIES 143 



As a further illustration of what is meant by a 

 between-race, mention may be made of the five-leaved 

 race of purple clover (Tri folium pratense) obtained by 

 de Vries, and developed by a process of selection. It 

 would appear that the plants occasionally found grow- 

 ing wild, which bear a single four-lobed leaf, usually 

 belong only to a half-race. De Vries was fortunate 

 enough to find two plants upon each of which several 

 of the leaves showed this anomaly, and from these, by 

 an elaborate process of selection extending over several 

 years, a race was obtained, the leaves of which in the 

 majority of cases showed five lobes, whilst some had 

 six or seven. Since, however, it appeared impossible 

 to get rid of a certain proportion of three-lobed leaves, 

 and equally so, on the other hand, to obtain leaves 

 with more than seven lobes, de Vries concluded that 

 his experiment exemplified the development of a mid- 

 race, and not that of a constant race or true variety. 



Some of the experiments upon which the above- 

 mentioned conclusions of de Vries are based are open 

 to the criticism that sufficient precautions do not seem 

 to have been taken to prevent intercrossing between 

 the selected plants and other types of different con- 

 stitution, and it is only just to mention that such cases 

 are usually pointed out by the author himself. In 

 these cases the possibility of cross-fertilization between 

 the novel type and normal members of the species from 

 which it was derived renders the conditions of experi- 

 ment closer to those obtaining in Nature ; but full pre- 

 cision in the interpretation of the results is thereby 

 sacrificed, and it will be of interest to have evidence 



