Trifolhmi Pratensc Quiiiqucfoliiim. 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.^ 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 eff"ected. Further, the character 

 can be improved by selection within the limits of varia- 

 bility in the new race, just as in tlic case of ])ure specific 

 characters. When once the furthest point in this direc- 

 tion has been reached, and this usually occurs after a 



^ Or at least revert as rarely as fonr-leavecl individnals occur in 

 the ordinary clover, which are in reality also partially ata\istic. 



