viii Preface 



power of an hypothesis assuming the existence in Nature of an 

 X-entity, additional to matter and energy but of the same cosmic 

 rank as they, and manifesting itself to our senses only through 

 its power to keep a certain quantity of matter and energy in the 

 continuous orderly ferment we call life. If those complicated and 

 regularly-recurring cycles of material and energy changes which 

 constitute the visible phenomena of life were mechanistically 

 self-originating, self-controlling, and self-surviving, then Nature 

 should be full of scattered fragments of such cycles, whereas she 

 is not. For everything in Nature has either all of the characteris- 

 tics of life, or else it has none of them; it is either alive, or it is not. 

 And there you have the chief argument of vitalism against 

 mechanism. 



Having thus explained, the best that I can, the spirit and scope 

 of this book, I turn to make my grateful acknowledgement to 

 those who have rendered kind aid in its preparation. For the 

 illustrations, in particular, I am indebted to many persons. For 

 the privilege of using the two dozen or more fine pictures from 

 Gray's Structural Botany and the Chicago Textbook, as acknowl- 

 edged with the cuts, I am indebted to the publishers of those 

 works, the American Book Company; and I have also been per- 

 mitted by the Doubleday Page Company to use figure 8, and by 

 the Bullard Company to use figure 15, from publications of theirs. 

 Further, a ready consent has been given by Professor G. F. Atkin- 

 son to my use of figure 118, and by Dr. C. C. Curtis, to my use of 

 figures 67 and 73, from books of theirs published by IMessrs, Henry 

 Holt and Compan}^ In addition, I have copied a number of 

 figures from various foreign works, notably those of Sachs, 

 Kerner, Strasburger and Kny, taking pains, however, to acknowl- 

 edge the sources with the cuts themselves. Further, I have made 

 use without special acknowledgement of a good many pictures 

 which have been copied so often as to have become a kind of 

 common property (viz., figures 17, 35, 94, 147, 149 to 161, 164, 

 166-7, 169-171), although these, together with certain others 



