Introduction. 9 



certain appendages and coverings, which in function may 

 be quite indistinguishable from others belonging to the 

 fruit. A seed, therefore, for our present purposes is the 

 one-seeded unit of dispersal. All our British fruits, with 

 the single exception of that of the Cornel, divide into such 

 one-seeded portions, which tend to be dispersed separately, 

 so that the young plants do not interfere with each other. 

 These units may be seeds in the strict botanical sense, or 

 they may be complete one-seeded fruits ; sometimes they 

 are stones or carpels, one-seeded, or at any rate with only 

 one of the seeds properly developed ; in other cases they 

 include the dried calyx, or other parts of the flower or 

 receptacle. Constant explanation would be needed if an 

 attempt were made to define botanically what part of the 

 fruit is referred to in each case — it is more convenient to 

 accept the perfectly understood popular usage. 



