vi Preface 



and sternly-preserved leisure for reflective concentration on the 

 matters it considers. At least, any value it may have for the 

 reader will be realized best through this mode of approach. 



As to the method of treatment in particular, I have sought 

 especially to interpret those phenomena of plant life which come 

 within ordinary observation and experience, penetrating just 

 deeply enough into each to make clear the principle of its opera- 

 tion, "the theory of the thing" in popular phrase; and some- 

 times that has taken me far and sometimes it has not. Thus is 

 explained the absence of some matters of high technical interest, 

 which lie, however, outside the experience of the general observer. 

 Where explanations are concerned, I have given the known ones 

 when there are any, and when these are lacking I have not 

 hesitated to supply suggestions of my own, though in a way 

 designed to show their hypothetical character. As to statements 

 of fact, I have meant to present only those which have acquired 

 the impersonal validity of science, for which reason I have omitted 

 a good many of the newest ideas, even at the risk of seeming not 

 to know them; for I have noticed that he who is too closely up to 

 date in science has later a good deal to unlearn. 



This deliberate conservatism is not, however, the inspiration 

 of my advocacy of Darwinian adaptation, for that is based upon 

 conviction as to its essential correctness. I am very well aware 

 that some eminently respectable people now consider adaptation, 

 except as an accident, an antiquated idea. I have myself expe- 

 rienced periods of this belief, but have always found myself back 

 to causative adaptation as the most rational explanation we 

 possess of the relations of living beings to their environment. 

 But while holding to the reality of adaptation as an historical and 

 causative process, I do not by any means suppose that all plant 

 phenomena are explainable on this basis; and in this book I have 

 tried to sort out the numerous influences at work, and to show 

 which phenomena are best explained by adaptation, which by 

 mechanical causation, and which by others of the possible forma- 



