ADAPTATIONS OF SEEDS AND FRUITS. 221 



prevalence on our river banks of oaks, hickories, and maples is 

 also very noticeable. Again, ocean currents are of great impor- 

 tance in distributing plants. The cocoanut, buoyed by its loose 

 husk and protected by an impenetrable shell, floats in the sea 

 until it is brought often to some coral island where it may grow. 

 Many small seeds are also conveyed by ocean currents, and it is 

 very probable that they retain their vitality, for Mr. Darwin has 

 recorded some interesting experiments showing that a good pro- 

 portion of seeds can withstand injury from salt water for a con- 

 siderable length of time. The action of freezing water, as mani- 

 fested in frost, has the well-known effect of freeing nuts from 

 their protecting envelopes; and frozen water, in the shape of 

 glaciers and icebergs, is of a little importance in transporting 

 seeds. It is possible that during the Glacial period seeds were 

 conveyed from place to place incased in ice. 



Of all devices for dispersion the most remarkable are those by 

 which the aid of animals is secured, and this aid is so valuable 

 that plants spare no expense to obtain it. Usually animals are 

 well paid for their services, but many plants, however, do not 

 hesitate to deceive their benefactors by all sorts of trickery. 

 This latter class, though, has not been nearly as successful as the 

 others in the struggle for existence. 



It is now well known that what are popularly called " fruits " 

 exist for the mutual benefit of plants and the lower animals not 

 for man. And it is generally believed that these fruits have 

 developed their attractive qualities through natural selection. 

 The results reached by man in selecting and propagating the best 

 varieties of fruits are the strongest grounds for thinking that 

 these fruits were once evolved from very crude conditions through 

 similar selection by the lower animals, particularly birds. Such 

 fruits, for instance, as by natural variation became at all agree- 

 able to birds would be sought out by them, to the exclusion of 

 less attractive fruits. In consequence, the favored fruits would 

 stand better chances of setting seeds than would their less favored 

 companions. Variations being transmitted from parent to off- 

 spring, it is reasonable to suppose that favorable variations would 

 become still more favorable by further selection, until, by the 

 accumulation of even slight variations through geologic ages, 

 there would result fruits highly attractive to certain animals by 

 their color, perfume, and taste. In the mean time, fruits possess- 

 ing unfavorable characteristics have for this very reason been 

 exterminated, or else have attained a less degree of success than 

 the others. 



Insects are the lowest animals known to assist in seed dissem- 

 ination. Mr. Darwin tells us of locust excrement containing 

 seeds which grew when planted. Considering that locusts often 



