INTRODUCTION. 



offers certain problems in capillary phenomena. Recent 

 researches have shown that these problems are compli- 

 cated by the behaviour of the air-bubbles above referred 

 to, and which are entangled between the water-columns 

 in the various tubes, of different calibre, length, and 

 substance, of which the wood is constructed. 



6. BY THE BOTANIST, FORESTER, ETC. 



The scientific botanist sees in any piece of wood a 

 complex structure cut up into tubes of various kinds, 

 and differing in length, diameter, and the thickness of 

 their walls. 



These tubes may be empty — i.e. contain only air — 

 or more or less filled with certain substances of the 

 nature of starch, sugars, resins, etc. They may also be 

 grouped in an immense variety of combinations, and the 

 directions of their longer axes may be either coincident 

 with that of the long axis of the stem or across it. 



The closer microscopic examination of these tubular 

 elements of the wood discloses various irregularities or 

 markings on the walls of these tubes, and long experience 

 of many such examinations convinces him that certain 

 types of such markings constantly recur in different 

 timbers. The botanist is consequently enabled to classify 

 or group the various tubular elements into a few classes, 

 or types, to which he gives technical names. 



The botanist is also concerned with the origin, or 

 development, of these elements, and finds that they 

 arise in all woods from the same primary element, and 

 follow the same course of development in each and 

 every case. 



Such studies have led him further, however, and he 

 has had to frame conceptions of the ultimate structure 



