16 TBOHNIOAI. PROPERTIBS OF WOOD. 



-wood of the stem than the more porous wood of the roots, slow- 

 grown conifer wood than faster-grown specimens, and so on. 

 Elasticity is increased by slow seasoning ; hence killing a tree by 

 girdling is injurious to elasticity. 



The following scale of elasticity may be adopted : — 



1. Extremely elastic — bamboos, canes. 



2. Very elastic — Grewias, sundri, Anogeissus latifolia. 



3. Elastic — Diospyros spp., sissu, 



4. Pretty elastic — teak, mango, tun. 



5. Slightly elastic — deodar, Hardwickia binata, semal. 



6. Very slightly elastic — Boswellia serrata, silver fir. 



Section V. — Aptitude fob fission. 



All woods are more or less fissile, i.e., capable of being split 

 down their whole length when a wedge is forcibly driven along 

 between the fibres. The ease or dif&culty with which a piece of 

 wood can thus be split depends on five several circumstances as 

 follows : — 



I. The structure of the wood. — The straighter and longer and 

 more parallel the fibres are, the more easily will the wood split, e.g., 

 bamboos, canes, conifers, teak, &c. Hence for one and the same 

 species the faster-grown the specimen, the more easily will it split. 

 All breaks of continuity of the fibres, such as knots, branches, 

 and wound scars, increase the difficulty of splitting ; in other 

 words, canopy-grown trees with long, clean boles and a high re- 

 stricted crown furnish the best wood for fission, and trees with 

 low spreading crowns the worst. Wood from the branches and 

 roots, being more knotty and crooked and twisted, is more difficult 

 to split than the wood of the stem ; and the most difficult of all to 

 split is the wood in the region of the root-collum, from which all 

 the main lateral roots of the tree take their rise. The medullary 

 rays, by their thickness, length and depth, influence very con- 

 spicuously the aptitude of wood for fission, as all woods split most 

 easily in the direction of the rays. Owing to the presence of large 

 rays, woods, which like the oaks, would otherwise be extremely 

 difficult to split, are among those most easily fissile. Great number, 

 by forcing the fibres to extend evenly and straight, makes up for 

 smallness and even minuteness of the rays, as in the case of the 

 conifers. The degree of coherence between the fibres and the 

 medullary plates also influences the fissility of a wood. The coher- 

 ence between the concentric rings of wood is very much greater 

 than that between the fibres and medullary plates. In old in- 



