100 A NATURALIST IN THE PACIFIC chap. 



means of dispersal either for plants or animals. With regard to 

 plants, she makes no direct provision for the distribution of their 

 fruits or seeds. If she had done so, she would have employed 

 some uniformity in her methods, as in the instance of the means 

 of reproduction ; whereas the modes of dispersal are almost infinite 

 in their variety. When I say that Nature makes no direct pro- 

 vision for the dispersal of plants and animals, I mean not in the 

 sense that a bird is adapted for an aerial life, or an aquatic plant 

 for a more or less submerged existence. That a bird is often able 

 to distribute its kind over a great area is the " accident " of its 

 conditions of existence. In a similar way the wide distribution of 

 the " ticks " that they carry round the world is due to the para- 

 sitical habits of these insects, habits that have been acquired with- 

 out any view to their mode of dispersal by birds. 



Similarly it cannot be said of seeds or fruits that are transported 

 ty birds, whether adhering to their plumage by means of hooks or 

 hairs, or through some viscid excretion, or inclosed in soil adhering 

 to the feet or legs, or carried in the stomach and intestines, that 

 Nature has made any special provision for their dispersal. The 

 dispersing agencies take advantage of certain capacities or charac- 

 ters of a seed or fruit that have been developed in the plant for 

 quite other reasons and in conformity with quite other principles. 

 There may be mentioned as examples the mucosity of seeds, the 

 fleshiness of fruits, the occurrence of hairs and prickles, &c. Yet 

 as far as their connection with dispersal is concerned, such capacities 

 and characters are blind results in the history of the plant's 

 development, the dispersing agencies making use of what was 

 not intended for them. 



"Adaptation to definite life-purposes," as Sachs terms it 

 {Physiology of Plants, 1887, p. 122), is seen everywhere ; but it 

 is adaptation restricted to the organism's conditions of existence, 

 It is not conceivable, as I have said, that an organism can be 

 adapted to conditions outside its environment. If there is such 

 a seeming adaptation, it is but a blind result, the accidental out- 

 come of collision or contact between two sets of conditions. If 

 we represent a number of these sets of conditions by several circles 

 gradually increasing in size until they encroach on each other, we 

 find that the circles lose their form and acquire a polygonal shape. 

 All characters seemingly connected with modes of dispersal have 

 only this indirect relation to such agencies ; and their utility in 

 these respects is an accident in the plant's life. They have not 

 been acquired in connection with the dispersing medium, but are 



