. Canadian forest industries July-December 1923. Lumbering; Forests and forestry; Forest products; Wood-pulp industry; Wood-using industries. CANADA LUMBERMAN effect manifested by a decrease in the size of those wood cells which are formed during the latter part of the growing season. Ail Canadian timber trees which add a new wood layer yearly display the successive layers of wood in transverse sections of the trunk as a series of ccnsentric rings. Each ring, representing as it does the amount of wood added in one year, is called an annual ring. In the spring growth is fast and the cells forme
. Canadian forest industries July-December 1923. Lumbering; Forests and forestry; Forest products; Wood-pulp industry; Wood-using industries. CANADA LUMBERMAN effect manifested by a decrease in the size of those wood cells which are formed during the latter part of the growing season. Ail Canadian timber trees which add a new wood layer yearly display the successive layers of wood in transverse sections of the trunk as a series of ccnsentric rings. Each ring, representing as it does the amount of wood added in one year, is called an annual ring. In the spring growth is fast and the cells formed at that time are frequently of large diameter. Those formed later in the season (during the summer) however, are of smaller diameter and have thicker walls. The wood formed in summer, being composed of cells with comparatively small cavities, is denser and harder than the wood formed at the beginning of the growth period. As during the winter the tree is dormant and no additional growth takes place the successive annual layers are usually differentiated by the contrast in texture and color between the hard summerwood of a previous ring and the contiguous softer springwood of the subsequent year's growth. Hardwoods Divided Naturally into Two Classes by Pore Arrangement There are two main classes of hardwoods which are characterized by: the arrangement of the vessels or pores. Transverse sections of Figure 4 A Figure 3 B. Ash—Transverse Sections x 15 Ring porous wood of three different rates of growth. A—With wide ring is from wood weaker than sample represented by B. C—With narrow rings and large pore content is weakest. one class show the pores nearly uniform in size throughout the annual ring. This condition is typified in the photograph of birch cut transversely, shown in Figure 1A. This illustration, showing the eyid view of the polished surface of a portion qf a "birch log (magnified 19 diameters) shows the distribution of pores known as diffuse arrangement. Fi
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectforests, bookyear1923
