40 PLANT LIFE. 



sugar is the usual form in which plant food (the 

 carbon, hydrogen, and oxygen) is carried about 

 the plant : the fruit jellies are due to a form of 

 cell-wall substance, '' pectose" which is developed chiefly 

 in fleshy fruits. The original fleshy fruits have been 

 probably greatly improved by the constant selection 

 of birds or of other animals, which have sought out 

 those they preferred. There is, however, considerable 

 difficulty in understanding certain cases. Such fruits 

 as Guelder Eose ( Viburnum) appear to have been in 

 existence in the chalk period, before birds were at 

 all common, or widely distributed. Possibly the Ptero- 

 dactyls, some of which were not larger than a pigeon, 

 lived upon fruits ; but, at present, so many animals 

 are frugivorous that there is no difficulty in under- 

 standing the prevalence of fleshy fruits. In addition 

 to birds, the flying-foxes or fruit-eating bats, and many 

 mammalia are largely dependent upon fruits for their 

 food supply. There is, certainly, a great probability that 

 these animals selected fleshy fruits, and thus aided in 

 their development, just in the same way that selection 

 by man has assisted in the formation of the varieties of 

 orchard fruit now in existence. 



In different fruits the fleshy part is formed from 

 very different parts of the flower, and the botanical 

 names of fruits, which are given according to the part 

 modified, are very numerous, and occasionally very 

 obscure. Hence in most text-books much space is 

 given to their description. To give information on 

 such points does not enter into the scheme of this 

 work. 



It is easy, however, to show that the fleshy part may 

 be produced from almost any part of the flower, and 

 also that the seedling-protection varies in a similar way. 



