Trifolinm Pratcnsc Quinque folium. 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% 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 entirely 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- 
erons 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 anomaly but had not succeeded in destroying or 
even in concealing the fact that the culture belonged to 
the pentamerous race. 
I also made an experiment on the influence of ex- 
ternal conditions on the development 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 
onwards. In the former case we determine the effect 
on the grown plant. This is however seldom great, inas- 
