CH. II.] ITS PROPERTIES AND VARIETIES. 21 



Now, there is no doubt that the structure of the 

 wood as formed by the cambium is the chief factor in 

 deciding these technological characters : it is not the 

 only factor, but it is the most important one. Conse- 

 quently no surprise can be felt that those who are 

 interested in timber have of late years turned their 

 attention to this subject with a view to ascertain as 

 much as possible about this structure, and to see 

 whether it can be controlled or modified, what dangers 

 it is subject to, and how far a classification of timbers 

 can be arrived at. The more the subject is studied, 

 the more interesting and practically important the 

 matter becomes. The results already obtained (though 

 the study is as yet only in its infancy) have thrown 

 light on several burning questions of physiology 

 as witness the researches of Sachs, Hartig, Elfving, 

 and Godlewski, on that old puzzle, to account 

 for the ascent of water in tall trees. The study is, 

 moreover, of first importance for the comprehension 

 of the destruction of timber, due to " dry-rot " and 

 the parasites which cause diseases in standing trees, 

 as is shown by the brilliant researches of Prof. R. 

 Hartig on the destruction of timber by Hymenomy- 

 cetes ; and again as yielding trustworthy information 

 as to the value of different kinds of timber in the arts, 

 and enabling us to recognize foreign or new woods 



