268 THE BIOLOGY OF THE SEASONS 



that persists after pollination has been effected that is to 

 say, after the possible seeds or ovules have become real 

 seeds. In most cases a fruit may be described as the 

 ripe seed-boxes, or as a collection of ripe seed-boxes, with 

 or without extra parts, such as the fleshy top of the flower- 

 stalk or a persistent calyx. In some cases, as in common 

 cereals, where a single seed fills the seed-box, fruit and 

 seed are practically identical, though the theoretical 

 difference remains clear. In order to understand the 

 different kinds of fruits, which represent different solutions 

 of a very interesting problem, we must also notice that 

 the wall of the fruit (the pericarp) often consists of several 

 layers, very different from one another. Thus in the 

 familiar case of a plum there is the firm outside skin 

 (epicarp), which keeps bacteria and moulds out until it 

 gets even a slight wound ; there is the fleshy pulp (meso- 

 carp), which is all loss to the parent plant, but attracts 

 the birds, which scatter the seeds ; and there is the very 

 hard "stone" (endocarp), which effectively preserves 

 the seed within a living embryo from being digested 

 in the bird's food-canal, from being frost-bitten in the 

 ground, from premature germination, and from other 

 risks. 



The use of the fruit is to secure a measure of success for 

 the seeds ; but this requires analysis, (i) The seed is an 

 embryo plant with a legacy of nutritive material ; it grows 

 within the ovule from a microscopic egg-cell fertilised by 

 a pollen-grain ; it is, for a time, a very delicate young life. 

 One use of the fruit is to protect the developing seed from 

 bad weather. (2) Even when the seeds are fully formed 

 and have attained to great tenacity of life, there is need 

 for the fruit's protection, for instance, against small seed- 

 eating animals, such as boring beetles, or against larger 

 creatures, such as birds and rodents, which devour and 



