PKEFACE. 



matter; but the author ventures to hope that not only is 

 the book novel in scope and style, but that certain views 

 therein expressed are original and may prove of service. 

 Thus, in the introductory chapter, the account of the 

 distribution and relative abundance of the elements con- 

 tains some ideas not, so far as he is aware, to be found 

 elsewhere. Chapters IV., X., and XIV., too, will be found 

 to contain matter not generally available. 



Osmosis and diffusion appear to be commonly regarded 

 by botanists as synonymous terms, and much confusion 

 seems to exist as to the parts which osmotic pressure and 

 diffusion play in the processes of plant life. In the tenth 

 chapter an attempt has been made to explain the essential 

 differences between free diffusion through a porous mem- 

 brane and the setting up of osmotic pressure when 

 solutions of different concentration are separated by a 

 semi-permeable membrane, and to point out the applica- 

 tion of the knowledge of these phenomena to the particular 

 case of a plant's roots. 



In the description of Brown and Escombe's valuable 

 researches 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 1899, 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. Most of these processes 

 are such as the author himself uses, and certain little 

 modifications which he has found useful are described. 



