8 INTRODUCTION [CHAP. i. 



have therefore done, and am more than ever 

 convinced that while Mr Reid's arguments are 

 professedly hypothetical only, they do not in the 

 least conform to what present-day ecologists 

 are agreed upon, i.e., as to the true cause of the 

 changes of structure and function which occur 

 in plants as soon as the environment is changed. 

 In 1876 Darwin had become a true ecologist. 

 In this year he wrote to Professor Moritz 

 Wagner as follows: 



"The greatest mistake I made was, I now 

 think, I did not attach sufficient weight to the 

 direct influence of food, climate, etc., quite inde- 

 pendently of natural selection. When I wrote 

 my book, and for some years later, I could not 

 find a good proof of the direct action [i.e., in 

 producing definite variations] of the environ- 

 ment on the species. Such proofs are now 

 plentiful." 1 



Plant ecologists, as modern botanists are called 

 who " study " plants " at home," i.e., as growing 

 wild in their various sorts of physical conditions, 

 are accepting "Adaptation" by response as 

 a proved fact. Germany, France, Denmark, 

 the United States, South Africa, abound with 

 ecologists. A complete change of front has 

 taken place within the last twenty years ; but 

 as Darwin himself was the first to profound 

 this view, I called it " The True Darwinism." 



1 " Life and Letters," vol. Hi., p. 159. 



