. Wood; a manual of the natural history and industrial applications of the timbers of commerce. Wood; Timber. 30 OF WOOD IN GENERAL broad-leaved trees no such regularity of radial arrangement of elements as characterizes the simple wood of conifers. In the cambium region, it is true, owing to the repeated regular tan- gential divisions, the cells not only appear rectangular m a trans- verse section, but are also in regular radial rows ; but in the xylem itself this regularity is disturbed by the different diameters attained by the various elements as they become fully formed. In Oak, for examp
. Wood; a manual of the natural history and industrial applications of the timbers of commerce. Wood; Timber. 30 OF WOOD IN GENERAL broad-leaved trees no such regularity of radial arrangement of elements as characterizes the simple wood of conifers. In the cambium region, it is true, owing to the repeated regular tan- gential divisions, the cells not only appear rectangular m a trans- verse section, but are also in regular radial rows ; but in the xylem itself this regularity is disturbed by the different diameters attained by the various elements as they become fully formed. In Oak, for example, the aimual rings are marked in a cross- section by the large and conspicuous pores, or sections of the vessels, which occupy the greater part of the spring wood of each ring (Fig. 27). On a radial section the layers appear as parallel. P£G 26 —Transverse section of Beech (Fagus syhahca) Magnified 100 times a, narrow pitli ray , &, broad pith-ray, c, boundary of an annual ring Tho largo pores are transverse sections of vessels (tracliese) Tlie tlnck-walled elements with narrow lumma aie wood-fibres; those with thinner walls and wider lumin-x, wood parenchyma or trachexds (From Hartig s Timbers and Jwiv to know them, by permission of Dr Somorville and Mi David Douglas ) stripes, and on a tangential one as broader and less parallel stripes ; but, whilst in coniferous woods the dark bands were denser summer wood, in this case the darker parts are produced by the vessels in the spring wood, the more uniform fibres of the summer wood appearing lighter. Vessels, tracheids, and fibres formed in spring have larger diameters and thinner walls than those formed in autumn, which fact produces much of the distmctness of the annual rings. In timbers with well-marked rings the distinctness of these rings may either be due, as in Oak, Ash, Teak, etc., to the contrast between wood with numerous large vessels and that with fewer or smaller ones ; or, as in Birch, Maple, Horse-chestnut
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