SUCCULENT FRUITS 371 



bodies, in the mud adhering to their feet and so on. 

 An almost incredible number of different seeds and 

 small dry fruits may often be found in the pockets and 

 seams of the clothes as well as on the boots of men who 

 spend much time in the open country. 



In the case of succulent fruits which are sought and 

 eaten by birds and mammals, the seeds, which are 

 protected by an indigestible covering, are often swallowed 

 and voided at a distance. The attractive succulent 

 part of the fruit may be the inner layers of the pericarp 

 (melon, raspberry, date, etc.) or special ingrowths from 

 the pericarp (orange) , or it may be the perianth leaves 

 (mulberry), or the receptacle of the flower which has 

 become fleshy in the fruit (strawberry, apple), or of 

 the whole inflorescence. The seeds of such fruits are 

 nearly always protected by a layer of hard- walled cells, 

 which resist the digestive enzymes secreted in the 

 alimentary canal of the animal and thus prevent 

 the substance of the seed from being digested. In 

 most cases this is the testa of the seed, but when the 

 succulent part of the fruit is the receptacle or perianth, 

 it is the whole pericarp (strawberry, apple, fig, mulberry), 

 or where the outer layers of the pericarp alone are 

 succulent, it is the inner layer, i.e. the " stone " of 

 " stone fruits/' the seed itself (the kernel) being digestible 

 once the stone is removed. 



Very often the seeds of succulent fruits stick to the 

 beaks of birds pecking at the fruit, because they are 

 surrounded by a sticky pulp, and are later rubbed off 

 or fall off when the pulp dries. The seeds of mistletoe 

 are distributed in this way. The birds peck at the 

 mistletoe berries and the seeds stick to their bills. 

 They clean their bills by rubbing them on the bark of 

 tr ees, and the seeds catch in the crevices, where they 



