412 PLANT PHYSIOLOGY 



do so is because with our unique protoplasm, having its own par- 

 ticular heredity and environment, there was no other course open. 

 No other decision was possible with the organism which we pos- 

 sess, — an organism with an environment and a heredity unlike 

 that of any other individual in the world. Man is an organism 

 like all others. Reason is simply the result of the play of external 

 circumstances upon a physicochemical machine. There is appear- 

 ance of free will without the substance because we are unaware 

 of the causative chain of events which has predetermined the 

 decision. Our actions are, hence, largely tropistic. We go towards 

 food, warmth, and water in much the same way that the lower 

 animals and plants do. The chief difference is in the mechanism 

 through which the stimulus must act; its greater complexity ne- 

 cessitates a more circuitous and less visibly direct route. Accord- 

 ing to the conception of mechanism, the principle involved and 

 the results obtained are the same throughout the organic world; 

 alcohol increases the phototropic sensitivity of plants (Monte- 

 martini, 1926), and even though the inebriate does not seek the 

 lamp-post because he is positively phototropic, his action may 

 be the result of tf/i^raotropism ! The emotions are likewise the 

 result of physicochemical laws which, to the mechanist, are in 

 the same category as the reactions which result in the nourish- 

 ment and reproduction of the individual. 



Modern Vitalism.— In these mechanistic mazes, hypotheses and 

 fact have not always been clearly distinguished, with the result 

 that many elementary students have not realized just how far 

 the mechanists have been able to prove their doctrines. The vital- 

 ists have rebelled against what to them is an unwarranted as- 

 sumption. They are quite willing to follow the results of ex- 

 perimental research and to accept the findings of the laboratory 

 method, they say, but they find themselves unwilling to admit 

 that because certain processes are physicochemical all must be. 



Among the modern vitalists a few outstanding figures should 

 be mentioned. Driesch has been especially impressed by the proc- 

 esses of differentiation in growth and the various stages in the 

 formation of organs. Why should development assume this or- 

 derly and progressive series of changes? He saw in organisms a 

 driving force which he called an entelechy that guided the growth 

 of the individual. John Calvin placed the forces which guided 

 man's destiny without him, but nevertheless put him in a posi- 



