2i6 Flowers and their Pedij^rees. 



many points of structure and function. The first of 

 the two branches in question is that of the plum-tribe ; 

 the second is that of the pears and apples. Each 

 presents us with some new and important modifica- 

 tions of the family traits. 



Of the plum tribe, our most familiar English 

 examples, wild or cultivated, are the sloe or black- 

 thorn, with its descendant the garden plum ; as well 

 as the cherry, the apricot, the peach, the nectarine, 

 and the almond. All these plants differ more or less 

 conspicuously from the members of the central group 

 which we have so far been examining in their tree- 

 like size and larger trunks. But they also differ in 

 another important point : each flower contains only 

 one seed instead of many, and this seed is inclosed in 

 a hard bony covering, which causes the whole plum 

 tribe (except only the almond, of which more anon) 

 to be popularly included under the common title 

 of ' stone-fruits.' In most cases, too, the single seed 

 is further coated with a soft, sweet, succulent pulp, 

 making the whole into an edible fruit. What, now, 

 is the reason for this change } What advantage did 

 the plant derive from this departure from the ordinary 

 type of rose-flower and rose-fruit ? To answer this 

 question we must look at one particular instance in 

 detail, and we cannot do better than take that well- 



