608 THE POPULAR SCIENCE MONTHLY, 



lating carbon, under the influence of solar energies, show a tendency 

 to assume tints other than green. This tendency would, of course, be 

 checked by natural selection in those seeds which, like nuts, are de- 

 stroyed by animals, and so endeavor to escape their notice ; while it 

 would be increased by natural selection in those seeds which, like 

 fruits proper, derive benefit from the observation of animals, and so 

 endeavor to attract their attention. But it is noticeable that fruits 

 themselves are sour, green, and hard, during their unripe stage that 

 is to say, before the seeds are ready to be severed from the mother- 

 plant ; and that they only acquire their sweet taste, brilliant color, 

 and soft pulp, just at the time when their mature seeds become capa- 

 ble of a separate existence. 



Perhaps, however, the point which most clearly proves the purely 

 functional origin of fruits is found in the immense variety of their struct- 

 ure, a variety far surpassing that of any other vegetable organ. It 

 does not matter at all what portion of the seed-covering or its adjacent 

 parts happens first to show the tendency toward succulence, sweetness, 

 fragrance, and brilliancy. It serves the attractive purpose equally well 

 whether it be calyx, or stalk, or skin, or receptacle. Just as, in the case 

 of flowers, we found that the colored portion might equally well con- 

 sist of stamens, petals, sepals, bracts, or spathe so, but even more 

 conspicuously, in the case of fruits, the attractive pulp may be formed 

 of any organ whatsoever which exhibits the least tendency toward a 

 pulpy habit, and an accumulation of saccharine deposits. 



Thus, in the pomegranate, each separate seed is inclosed in a juicy 

 testa or altered shell ; in the nutmeg and the spindle-tree, an aril or 

 purely gratuitous colored mass spreads gradually over the whole inner 

 nut ; in the plum and cherry, a single part, the pericarp, divides itself 

 into two membranes, whereof the inner or protective coat is hard and 

 stony, while the outer or attractive coat is soft, sweet, and bright- 

 colored ; in the strawberry, the receptacle, which should naturally be 

 a mere green bed for the various seed-vessels, grows high, round, pulpy, 

 sweet, and ruddy; in the rose, the fruit-stem expands into a scarlet 

 berry, containing the seed-vessels within, which also happens in a 

 slightly different manner with the apple, pear, and quince ; while in the 

 fig, a similar stem incloses the innumerable seeds belonging to a whole 

 colony of tiny blossoms, which thus form a compound fruit, just as the 

 daisy-head, with its mass of clustered florets, forms a composite flower. 

 Strangest of all, the common South American cashew-tree produces its 

 nut (which is the true fruit) at the end of a swollen, pulpy, colored 

 stalk, and so preserves its embryo by the vicarious sacrifice of a falla- 

 cious substitute. These are only a few out of the many ways in which 

 the selective power of animals has varied the surroundings of different 

 seeds to serve a single ultimate purpose. 



Nor is any plan too extravagant for adoption by some aberrant 

 species. What seed-organ could seem less adapted for the attraction 



