Latent Characters 235 



nut has in some instances such evident protu- 

 berances on the valves of its fruits, that it may 

 seem doubtful whether it is a pure and stable 

 variety. 



Systematic latency may betray itself in dif- 

 ferent ways, either by normal systematic 

 marks, or by atavism. With the latter I shall 

 deal at length on another occasion, and there- 

 fore I will give here only one very clear and 

 beautiful example. It is afforded by the com- 

 mon red clover. Obviously the clovers, with 

 their three leaflets in each leaf, stand in the 

 midst of the great family of papilionaceous 

 plants,the leaves of which are generally pinnate. 

 Systematic affinity suggests that the " three- 

 leaved " forms must have been derived from 

 pinnate ancestors, evidently by the reduction of 

 the number of the leaflets. In some species of 

 clover the middle of the three is more or less 

 stalked, as is ordinarily the case in pinnate 

 leaves ; in others it is as sessile as are its neigh- 

 bors. In a subsequent chapter I will describe a 

 very fine variety, which sometimes occurs in the 

 wild state and may easily be isolated and culti- 

 vated. It is an ordinary red clover with five 

 leaflets instead of three, and with this number 

 varying between three and seven, instead of be- 

 ing nearly wholly stable as in the common form. 

 It produces from time to time pinnate leaves, 



