44 Mr. Arthur Deane on 



during the growing season, at that particular place, cells similar 

 to the summer ones will appear throughout the season, but if the 

 pressure of the bark is relieved in summer by means of longitudinal 

 cuts, then at those places, wood like the springwood will be 

 formed. During the winter months the cambium is inactive, 

 and this sudden cessation of growth causes a boi'der line between 

 the rings while the transverse pressure becomes reduced by the 

 formation of cracks and fissures in the bark. But luitrition is 

 also intimately associated with the formation of this contrasting 

 tissue. In the following early spring with the released pressure, 

 caused by the cracked and fissured bark, the reserve food, which 

 is chiefly starch, and stored in the trunk, provides the cambium 

 with its first supply of food and it at once commences to renew 

 its activity, to form a lax thin-walled loose tissue. Later in the 

 season with a plentiful supply of rich nitrogenous food the 

 protoplasm plasters on the inner walls of the cells (except at 

 certain points, to form pits) thick layers of a peculiar substance 

 (or substances) which become changed into woody material 

 known as lignin. What is wanted in structural timber is less of 

 the soft light springwood and more of the closely packed thick 

 walled summerwood, the latter having considerable influence 

 upon the hardness of the timber. This, together with the 

 uniformity in texture and width of the annually formed rings, 

 are points of importance as to quality. What is wanted in 

 Softwoods are slow grown narrow rings to reduce the amount of 

 inner springwood, while in those Hardwoods having a porous 

 ring such as Oak, Chestnut and Elm, fast grown timber is 

 stronger and denser. 



In some woods the prominent spring and summer zones are 

 not so clearly defined, and may merge into each other as in 

 Beech, while in others there is no differentiation discernible. 



Care must be taken not to confuse with annual rings coloured 

 irregular wavy bands or rings which are seen on the cross section 

 of many heavy Indian and other tropical timbers. (Fig. 3). 

 These bands, which consist usually of soft tissue (wood cells or 



