4 INTRODUCTION. 



differ with authorities. A variety includes individuals differing 

 slightly from accepted species. Its name when exi is part 

 of the specific name. Quercus robur var. pedunculate 

 specifies a variety (pedunculate) of "red" or strong (robur) 

 oak (Quercus). A variety of one botanist is sometimes a c 

 tinct species of another. 



Information relating to wood must include some information 

 relating to the tree. 



A tree has been defined* as "a perennial plant which 

 from the ground with a single, permanent, woody, self-support- 

 ing trunk or stem ordinarily attaining a height at least twenty- 

 five or thirty feet." 



A tree has three principal parts or systems: they are the 

 roots, the trunk, and the foliage. Roots and foliage are here 

 regarded only as they are means by which wood is manufactured. 

 The root system of a tree consists of large branch-roots that 

 enable the tree to stand firmly in the ground and small hair-roots 

 that emerge from the larger ones to gather moisture and chemi- 

 cals from the soil. The small roots are very sensitive and are 

 the primary portions of the system. The larger roots serve as 

 canals through which the fluids collected by the smaller ones 

 travel upward toward the trunk and foliage. 



The foliage of a tree separates carbon from the air and 

 prepares it to unite with the faintly mineralized water that 

 arises from the roots. The preparation of sap is thus com- 

 pleted by the foliage. The movement of fluids in a tree is a 

 continuous movement. Up and down currents move together; 

 the one in the inner sapwood and the other through the outer 

 sapwood. Sap does not rise in the spring and fall in the 

 autumn. 



The sap thus completed in the foliage descends through 

 the outer sapwood and deposits a layer of mucilage -like sub- 

 stance between the sapwood and the bark. This young 

 substance or cambium is shortly quickened into life. Cells 

 develop, some of which form a layer of new wood while others 



* Century Dictionary. 



