46 SYMBWGENESlti 



said that everything- is due to the plant, " I'eternel 

 preparateur de la vie." That its productions and stimulative 

 influences, however, are largely regulated according to animal 

 behaviour is well borne out by the startling potency in the 

 animal economy of the vegetable alkaloid poisons. The plant 

 disseminates death or life to the animal world according to the 

 degrees of symbiosis to which it is treated. Thus the plant 

 (though, of course, unconsciously) discharges for the animal 

 the function of providing the requisite chemical stimulations, 

 much in the same way as we. say the corpus luteum has deputed 

 to it within the mammalian organism the duty of providing 

 the essential chemical stimulation for the growth of the 

 embryo and the formation of the mammary gland. 



So, again, we saw that only where the wood-buds can per- 

 form their highest function is the flower-bud possible. 

 Similarly, only where the plants can perform their highest 

 work can the animals advance in physiological complexity. 

 Thus, I maintain, does plant-evolution determine animal 

 evolution, and thus it is that symbiogenetic differentiation 

 alone conduces to life. 



We can also understand why nuts, for instance, which are 

 chiefly the products of trees or shrubs of considerable longevity, 

 according to Dr. Wallace, are so largely eaten by mammalia 

 and birds. We can now understand that such food must have 

 been possessed of adequacy to stimulate progressive develop- 

 ment whether through new organs or otherwise. We can also 

 perhaps understand the reason why the sub-class Monotremata, 

 though they possess corpora lutea, have not been able to equal 

 the rest of the mammalian class in forming a placenta. They 

 are largely " in-feeders," i.e., depending more exclusively on 

 animal food, and are thus debarred from a proper, direct, and 

 living relation with the plant, whose productions they can at 

 best only obtain at second-hand. 



What emerges is, again, the transcendent importance of 

 nutrition in evolution. We can explain the rise of form as 

 largely determined and even p re-determined by nutrition. We 



