606 THE POPULAR SCIENCE MONTHLY. 



with the nut, to digest the actual seed itself would be fatal to the life 

 of the young plant. But fruits get over this difficulty by coating their 

 seeds first with a hard, indigestible shell, and then with a soft, sweet, 

 pulpy, and nutritious outer layer. The purely accidental or functional 

 origin of this covering is testified by the immense variety of ways in 

 which it has been developed. Sometimes a single seed has shown a 

 slight tendency to succulence in its outer coat, and forthwith it has 

 gone on laying up juices from generation to generation, until it has 

 developed into a one-seeded berry. Sometimes a whole head of seeds 

 has been surrounded by a fleshy stem, and the attention of animals has 

 thenceforward encouraged its new habit by insuring the dispersion of 

 its embryos. A few of the various methods by which fruits attain their 

 object we shall examine in detail further on ; it will suffice for the pres- 

 ent to point out that any property which secured for the seed dispersion 

 by animal agency would at once give it an advantage over its fellows, 

 and thus tend to be increased in all future generations. 



So, then, as birds, squirrels, bats, monkeys, and the higher animals 

 generally, increased on the face of the earth, every seed which showed 

 a tendency to surround itself with succulent pulp would obviously gain 

 a point thereby in its rivalry with other species. Accordingly, as we 

 might naturally expect, fruits, which have been developed to suit the 

 taste of birds and mammals, are of much more recent geological origin 

 than flowers, which have been developed to suit the taste of insects. 

 For example, there is no family of plants which contains a greater 

 number of fruity seeds than the rose tribe, in which are comprised the 

 apple, pear, plum, cherry, blackberry, raspberry, strawberry, quince, 

 medlar, loquat, peach, apricot, and nectarine, besides the humbler hips, 

 haws, sloes, and common hedge-fruits, which, though despised by lordly 

 man, form the chief winter sustenance of such among our British birds 

 as do not migrate to warmer climates during our chilly December days. 

 Now, no trace of the rose tribe can be discovered until late in tertiary 

 times ; in other words, no fruit-bearers appear before the evolution of 

 the fruit-eaters who called them into existence : while, on the other 

 hand, the rapid development and variation of the tribe in the succeed- 

 ing epoch show how great an advantage it derived from its tendency 

 to produce edible seed-coverings. 



But not only must these coverings be succulent and nutritious, 

 they must also be conspicuous and alluring. For the attainment of 

 these objects the fruit has recourse to just the same devices which had 

 already been so successfully initiated by the insect-fertilized flowers. 

 It collects into its pulpy substance a quantity of that commonly -dif- 

 fused vegetable principle which we call sugar. Now sugar, from its 

 crystalline composition, is peculiarly adapted for acting upon the ex- 

 posed nerves of taste in the tongue of vertebrates ; and the stimulation 

 which it affords, like all healthy and normal ones, when not excessive 

 in amount, is naturally pleasurable to the excited sense. Of course, in 



