PEEFACE TO THE FIRST EDITION V 



In the tenth chapter, 1 an attempt has been made to explain 

 the essential difference between true diffusion through a porous 

 membrane and the setting up of osmotic pressure when solu- 

 tions of different concentrations are separated by a semi-per- 

 meable membrane, and to point out the application of the 

 knowledge of these phenomena to the particular case of a 

 plant's roots. 



In the description of Brown and Escombe's valuable re- 

 searches on the manner in which carbon dioxide is assimilated 

 by plants, through the stomata of the leaves, the author has 

 ventured to explain the results by a method which he devised 

 in 1890, and which is based on the generally accepted kinetic 

 theory of gases. 



The book does not profess to be a laboratory manual, but 

 in several instances accounts of various analytical processes, 

 applicable to agricultural products, are given with a view of 

 enabling the reader to understand and appreciate the results 

 of analyses. Many of these processes are such as the author 

 himself uses, and certain little modifications which he has 

 found useful are described. 



The diagrams are of simple character, intended to show r , as 

 clearly as possible, the particular points desired. 



The author wishes here to express his indebtedness to many 

 friends for assistance in various ways: particularly would he 

 acknowledge the help of one of his students Mr. Herbert 

 Hunter who has kindly prepared the index. 



LEEDS, March, 1902. 



1 Now eleventh. 



