ECOLOGICAL 199 



conspicuously coloured fruits, yet it must be noted that many birds 

 seem to be colour-blind to bluish tints. Moreover many palatable 

 fruits are inconspicuous, though perhaps sometimes more obvious to 

 their animal consumers than to us. In all probability the frugivorous 

 bird's individual experience and association-forming counts for 

 much. Large "stones" are seldom swallowed; small seeds are some- 

 times digested; yet on the whole it seems justifiable to say that 

 many seeds are scattered by being swallowed by birds and mammals. 



Besides the methods of dispersal which we have mentioned there 

 are others of minor importance, but of much interest. Thus some 

 ants in carrying certain fruits to the nest lose them by the way; 

 squirrels forget some of the nuts they have hidden; earthworms 

 plant the seeds of various trees. 



For distant dispersal the most important agent is undoubtedly 

 the wind; but in the case of oceanic islands the water-currents are 

 even more important. Fifteen years after the Krakatoan eruption 

 (1883) had killed off all the plants on the island, fifty-three species 

 of seed-plants had established themselves. Of these 60 per cent., 

 chiefly shore forms, were carried by ocean currents; 32 per cent, by 

 the wind; 8 per cent, by animals. 



We have illustrated Plant Ecology in reference to sustenance, 

 environment, reproduction, and linkage with other organisms, and 

 our illustrations must suffice, although they are, of course, vfery far 

 from representing the whole field of inter-relations. They may serve, 

 however, to suggest the general idea that plants are continually 

 moving towards some betterment — towards more food and more 

 light, towards multiplication and mastery. The concept of purposive 

 endeavour, which is suggested by a study of the higher animals, and 

 is consciously verified in man, does not grip in the plant world, but 

 that is not to say that it is irrelevant. We must think of the plant 

 as if it were continually sending out tendrils which feel for support 

 and often find it. Whence it begins afresh. This is the ecological 

 picture ! 



THE BALANCE OF NATURE 



This old-fashioned phrase sums up many interesting facts which 

 show that Animate Nature is well-adjusted to keep agoing, and that 

 smoothly. Living creatures have been sojourning together on the 

 earth and in the waters under the earth for so many hundreds of 

 millions of years that they have become adjusted into a system, 

 which has staying power and is not always tumbling to pieces. 

 Their numbers and their claims have attained to some degree of 

 harmony, and though this is often disturbed locally or temporarily, 

 there is an automatic tendency to get back to a viable balance. 

 On the Scandinavian table-lands there are large numbers of little 



