INTRODUCTION 



many species of Oak in which the pore-ring fails altogether, 

 and even the annual ring is difficult to make out, while the 

 little strings of branching pores, along with their attendant 

 soft-tissue, are always present. . 



It is a singular fact that as the tree ages the size of its cells 

 and pores increases ring by ring and year by year, so that upon 

 the surface of a plank " cut on the quarter," i.e. in the plane of 

 the radius, very narrow pores lie near the pith and large 

 ones near the bark, with all intermediate sizes between. 

 Thus a plank may be " fine grained " in one part and " coarse 

 grained " in another, whereas if the plank is cut from the outside 

 of the tree (tangentially), the grain or size of the pores and cells 

 may be nearly uniform throughout. This increase in the size 

 of the pores and cells ceases at a certain age in each species 

 (40). The Oak and the Hickory exhibit this phenomenon 

 in a striking degree. (Compare Figs. 117, 125, 151 and 152.) 

 The tree at the period at which this increase stops may be 

 said to be in its prime, for the wood then produced 

 possesses greater strength, weight, tenacity, etc., than that 

 produced either before or after (40). From a timber merchant's 

 point of view this question of growth is an important one, and 

 it must be borne in mind that it is wood and not cavities that the 

 user of timber wants; the greater the proportion of pores, the 

 less wood and the less weight and strength the timber will possess. 



A slow grown piece of Oak is a mere succession of pore-rings, 

 i.e. of little tubes, whereas well and fast grown Oak has a large 

 proportion of hard woody ground-tissue outside the pore-ring, 

 in which the rapidly diminishing pores form a comparatively 

 restricted area. There is no strength in holes, and the fewer there 

 are the better. In Coniferous wood such as Deal, which is free 

 from true pores, the slowly-grown wood, unlike the faster-grown, 

 is small celled and dense. It is merely a question of solid matter 

 of which the weight supplies a good indication. 



The counting of the rings is not an infallible indication of age 

 even when they are counted at the butt of the tree. There are 

 causes which disturb the even succession, such as the destruction 

 of the leaves by insects during the growing period, in which case 

 the ring is prematurely closed ; much after the manner of the usual 

 Autumn cessation of growth. If, as is sometimes the case (the Oak 

 again is an excellent example), the tree has power to put forth 

 fresh leaves, the growth recommences with a pore-ring, or 

 other lax tissue, as in the normal spring zone. Thus two rings 

 arise instead of one for the same year. It has been suggested that 

 in tropical climates two independent seasons of growth may cause 

 two fresh rings every year, but the idea needs experimental 

 verification, though not of itself improbable. For the most part 



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