Trifoliiiin Pratcnsc Qidnqucfoliuiii. 51 



only not poorer in seedlings with compound leaves but 

 even slightly richer; they were therefore not chosen for 

 the continuation of the experiment. I chose the seeds of 

 three plants of 1896 which had given rise to no more 

 than 2-3^0 seedlings with compound primary leaves. 

 Atavistic seedlings only were transplanted, but in the 

 following summer (1897) even those bore some tetra- 

 pentamerous leaves, almost without exception. On the 

 other hand 6-7-merous leaves were almost entirelv ab- 

 sent, and the race had thus returned to the condition 

 described by the unilateral curve of the first year of the 

 experiment (1891-1892). Some plants produced noth- 

 ing but trifoliate leaves during the whole of the summer 

 and the following spring. 



In 1898 I made another culture of atavists from the 

 seeds harvested in 1897. This was therefore the third 

 atavistic generation. But two thirds of the generation 

 raised still consisted of plants with some tetra-pentam- 

 erous leaves, and therefore possessed this character in 

 a far higher degree of development than ordinary red 

 clover. This stringent, thrice occurring reversed selec- 

 tion had therefore considerably reduced the development 

 of the anomalv but had not succeeded in destrovine or 

 even in concealing the fact that the culture belonged to 

 the pentamerous race. 



I also made an exi)eriment on the influence of ex- 

 ternal conditions on the develo])ment of multipartite 

 leaves. There are two ways of dealing with experiments 

 of this kind ; we may either subject the different parts of 

 the same plant to diverse conditions of life or similar 

 samples of seed to diverse treatments from germination 

 ouAvards. In the former case w^e determine the effect 

 on the grown plant. This is however seldom great, inas- 



