PREFACE TO THE SECOND EDITION 



AFTER much hesitation I have at last resolved to accede to the requests 

 made to me, during several years, to undertake a new edition of my 

 ' Pflanzenphysiologie.' The revision has necessarily been such that what 

 is essentially a new book has been produced. Since the appearance of the 

 first edition, so much work has been done, and our physiological knowledge 

 has been so broadened and deepened, that it needed a full and complete 

 revision of the whole to give a correct idea of our present standpoint. In 

 spite of the changes and additions made, I have been able to retain the 

 general arrangement, which has proved to be an advantageous one in a text- 

 book intended only for those already possessing a knowledge of physiology. 

 Moreover the fundamental principles still remain the same. A comparison 

 between the two editions will show, especially as regards the introductory 

 portion, that the views and ideas, which formed the guiding principles in 

 the first edition have proved correct, and have met with increasingly wide 

 acceptance. 



The scope of the book has not been enlarged. As before, it deals only 

 with the fundamental principles of metabolism and the sources of energy, 

 using those terms in the sense defined in the Introduction (Chap. I). This 

 exclusive adherence to important features and general relationships has 

 naturally made it impossible to discuss, or even mention, every detail and 

 individual peculiarity, the significance of many of which is frequently 

 overestimated. Nor can a complete catalogue of all the physiological 

 literature be expected. Nevertheless I have attempted, as far as possible, 

 to deal with the whole of the literature which forms the basis of our general 

 knowledge, and to which its expansion is due. Still I am afraid that, in 

 spite of all my care, much has been forgotten or overlooked, especially 

 since, owing to the pressure of other duties, the time necessary for this 

 work has been obtained with difficulty. This has rendered it impossible 

 for me to study certain problems as deeply as I had wished. Nevertheless, 

 the influence of my own research will be felt in nearly every chapter, 

 although, for the most part, the investigations and experiments made under 

 my direction, or at my instigation, are not expressly mentioned. I have 



