264 SCIENCE PROGRESS 



mensurate with its capacity of service to the plant. It has 

 often been remarked that the evolution of the animal proceeded 

 pari passu with that of the plant ; but it has been less commonly 

 realised that the plant, too, has had to rely upon symbiotic 

 help, both vegetable and animal. Still less has it been recog- 

 nised that the symbiotic relation between plant and animal is 

 the indispensable norm of life in all orders, not excluding 

 even the mammalia or man. 



More than one writer on evolution has asserted symbiotic 

 adaptation to culminate with insect and bird. But mammalian 

 services to, and alliances with, the plant are numerous and 

 important, whilst special significance attaches itself to the fact 

 of the continuity of the symbiotic relation throughout evolution. 

 In man the plant has a conscious partner — one whose essential 

 intelligence may well be presumed to be subtly supported by 

 numerous plant influences. 



As regards primitive Symbiosis once more, that of the lichen 

 has been much investigated, and here the success of the part- 

 nership is striking enough. And so is the modification of the 

 stirp commensurate with the intimacy of the partnership 

 between alga and fungus, and indicative of the progressive 

 endowment of the protoplasm consequent upon Symbiosis. 

 The fact of such modification inclines one to the view that sexual 

 partnership constitutes a case of Symbiosis, early herma- 

 phroditic stages representing attached or primitive Symbiosis. 

 Physical attachment, however, is a mere detail ; the absence 

 of such attachment need not impair the reality of a sym- 

 biotic union. It is not likely that nature could have ever 

 forsaken a method of life as proven as Symbiosis. What other 

 method of evolution is there so ideally conducive to economy 

 and progress ? 



In the erroneous belief that only attached forms constitute 

 Symbiosis, the case of the lichen is usually looked upon as the 

 stock example of Symbiosis. What I would specially insist 

 upon are the facts of the healthiness, the longevity, and the 

 general usefulness and success of this compound organism, 

 far exceeding anything fungus and alga could achieve 

 singly. 



A similar case is represented by the symbiotic bacteria in 

 the soil, which are more resistant to unfavourable influences, to 

 disease, than the predaceous inhabitants of the soil. They, 

 too, are of immense usefulness to organic life generally. 

 Modern scientific agriculture is largely based upon facts of the 

 usefulness of symbiotic bacteria and their powers of resistance 

 to disease. According to Prof. H. F. Osborn, a bacteria-less 

 ocean and a bacteria-less earth would soon be uninhabitable 

 for either plants or animals, and bacteria-like organisms pre- 



