Trifolium Pratcnsc Quinque folium. 37 
half race. In a half race the latent or semi-latent character 
is very seldom visible, perhaps in one leaf or on one plant 
amongst many thousands, and after several years of se- 
lection it is only on isolated individuals that two or three 
specimens of the anomaly may be found. 
In the middle race, or eversporting variety as I call 
it in contradistinction to the half race, the anomaly is by 
no means so rare. Most of the leaves consist of from 
4-7 leaflets, and plants without such scarcely occur at all 
even in the absence of any selection. Trifoliate leaves 
are not wanting; indeed no plant is without them, par- 
ticularly in its early stages and on weak branches. 
On the other hand pure five-leaved or pure seven- 
leaved races do not as yet exist : I mean forms which 
do not revert. 1 There is no ground for supposing that 
we may not succeed, some time, in obtaining at least a 
constant seven-leaved variety. But for this to happen 
the right combination of unknown causes must chance 
to offer itself (see 2) ; and this has not yet occurred 
in the case before us. 
When a variable race has been found in nature the 
next step is to isolate it. And if, as is the case with red 
clover, isolated individuals of the species are sterile, two 
or three of them must be cultivated together, or if this 
is not possible one or several generations must be grown 
as a rule in order to purify the race of the effects of cross- 
ing. But this is easily effected. Further, the character 
can be improved by selection within the limits of varia- 
bility in the new race, just as in the case of pure specific 
characters. When once the furthest point in this direc- 
tion has been reached, and this usually occurs after a 
1 Or at least revert as rarely as four-leaved individuals occur in 
the ordinary clover, which are in reality also partially atavistic. 
