VI 



PREFACE 



physical explanation of the rise of water in trees. This 

 theory rests on the knowledge of a property of liquids, 

 which, although discovered in the middle of the last 

 century, was little recognised and seldom referred to in 

 physical literature. It now appears that a full appreci- 

 ation of this property is essential for the realisation of 

 the manner in which water is raised in plants and of 

 the meaning of the structure of trees as a mechanism for 

 lifting water. 



In the formation of the theory and in much of the 

 earlier work carried out to test its validity and to illustrate 

 its applicability, Dr. J. Joly and the author worked in 

 collaboration. The work on the cryoscopy of sap was 

 carried out with the help of Mr. W. R. G. Atkins, to whom 

 the author is further indebted for his help in reading the 

 proofs and for his useful criticisms. Prof. R. A. Gregory 

 the editor of this series of monographs has also kindly 

 supplied several valuable emendations and suggestions. 



Henry H. Dixon. 



School of Botany, 



Trinity College, Dublin. 

 1914. 



