CHAPTER IV. 



ON THE THEORIES ADVANCED TO EXPLAIN THE 

 ASCENT OF WATER IN TALL TREES. 



IT has often been remarked that no account exists 

 in any English work, of the recent views as to the 

 mechanism which lifts water to the top of tall trees, 

 or of the controversy which has been so eagerly 

 carried on for some years on this subject, and, con- 

 sidering the numerous interesting observations and 

 experiments which have been made in this connection, 

 some general account of the matter should be of in- 

 terest both to students and teachers. In view of the 

 necessity that some botanist should undertake the 

 task, and that it ought to be done soon because the 

 phenomena have so many bearings upon matters 

 now engaging the attention of biologists, I have 

 attempted it, especially because so many side-lights 



