134 VIGNETTES FROM NATURE. 



that one may say they are practically the 

 very self-same plant ; only in the almond, the 

 fruit has a hardish shell, while in the necta- 

 rine it has acquired a soft one through the 

 selective action of birds. Similarly, there is 

 a common English potentilla which exactly 

 resembles a strawberry in everything except 

 the fruit, and that is dry instead of being suc- 

 culent. Here we may fairly say that the straw- 

 berry is just such a potentilla, whose seed 

 receptacle has become juicy and red, through 

 having been eaten by birds, which aided in 

 dispersing its seeds. The old botanists made 

 the strawberry into a separate genus because 

 of this conspicuous difference ; but in reality 

 the difference is worth very little as an indi- 

 cation of distinctness, for the potentilla had 

 already acquired every distinctive trait of the 

 strawberry, save only this one noticeable trait 

 of a succulent fruit-stem, long before they 

 diverged from one another; and that one 

 peculiarity might be and actually was easily 

 acquired without any change in the general 

 habit of the species. 



