XI ADAPTATION AND MEANS OF DISPERSAL loi 



the products of the laws of growth and heredity, guided by a 

 determining agency, and acting within the organism's conditions 

 of existence. It is within these narrow limits that all evident 

 adaptations lie. In matters outside the conditions of the develop- 

 ment of seeds and fruits, the evolutionary or determining principle 

 " lets them go." Detached from the plant, they come in contact 

 with conditions for which they were never created. The predo- 

 minant power in Nature, that brings to a successful issue the 

 development of an organism, has its limitations, and this is one of 

 them, the evolutionary or determining influence being ever checked 

 and hampered by the laws of the inorganic world. 



I can only refer briefly to some of the reasons that have led me 

 to apply this view of the duality of forces in Nature to the subject 

 of plant-dispersal. The principles of evolution and adaptation 

 rule the world except in matters of dispersal. Take, for instance, 

 the fleshy fruits which the gardener often makes more attractive 

 to birds than they are in the wild condition. The result is cer- 

 tainly to increase their facilities for dispersal by birds ; but such 

 a result was as little intended by man as it was by Nature when 

 species of Cornus, Ficus, Prunus, Viburnum, and other genera 

 matured their drupes, berries, and fleshy fruits in the Cretaceous 

 epoch. 



Children are now taught in several excellent little books on 

 " Nature-Study " that fleshy fruits are specially adapted to be eaten 

 by animals to secure the distribution of the seeds. We read in one 

 book that plants produce these fruits " on purpose to be eaten," in 

 another that they are " intended to be eaten," and in a third that 

 the seed-coverings are adaptations, all with the ulterior object of 

 distribution by frugivorous animals. I must be pardoned if I 

 venture to express my dissent from these statements, more espe- 

 cially since they are made by authors from whom it might be 

 thought almost impertinent for me to differ. Yet authority can 

 be claimed for holding the opposite view. 



When the botanist speaks of " useless secretions " in a plant, he 

 is alluding amongst other things to the sugar and organic acids of 

 fruits. " How and why all these substances originate is," as Pro- 

 fessor Sachs observed in the work before quoted, " not known." It 

 is, however, suggested by Dr. Kerner, in his Natural History of 

 Plants (Engl. edit, i, 460—462), that such secretions, though useless 

 to plants, may exist for the purpose of alluring animals to assist in 

 seed-dispersal. There are some botanists, it may be remarked, 

 that would reject such a view of the nature of fruits. Dr. Stapf in 



