DEFECTS AND QNSOUNDXESS. 61 



[Also in ebony, in which all the pores are filled with a black 

 substance, — and in box-wood, where the annual zones are very narrow, 

 the wood-fibres have extremely small lumina and the small pores of 

 the vessels ai'e sparsely and evenly distributed. — Tr.] 



Other wood is uneven-grained as iu the case of coniferous 

 wood with strongly developed summer-wood, and woods wdtli 

 large medullary rays. As regards the direction in which the 

 w^ood is cut, the silver-grain occurs where the medullary rays are 

 shown in their broadest section on radial cuts of oakwood, and 

 the tangential cut shows the ends of the rays. 



Fine-textured woods are those which show freedom from knots, 

 fine or even grain, fine waviness, or other marks. As a rule, dense 

 broad-leaved species are more finely textured than porous woods, 

 and more easily polished. Coarse-textured woods are coarse- 

 fibred, light, porous woods, those with a considerable difference 

 between the spring- and summer-woods, and knotty wood. As 

 already stated, fashion makes a great difference in the relative 

 value of woods at different times. 



Section XI. — Defects and Unsoundness in Timber. 



The study of the diseases of woody plants belongs to Vegetable 

 Pathology and Forest Protection. Under Forest Utilization, 

 only the fractures, defects and abnormities of wood will be 

 considered which in any way permanently reduce the utility 

 of wood. 



Such defects of wood may be separated into two groups — 

 those resulting from abnormities in the connection or structure 

 of healthy wood-fibres, and those resulting from disease. 



1. Defects in SoiDid l]\)od. 



(a) Heart-shake. — Heart-shake consists of radial clefts in the 

 timber proceeding from the pith and extending more or less 

 towards the sapwood and up the stem. The defect is termed 

 star-shake when there are several such clefts, and simple heart- 

 shake when there is only one cleft extending in a line across 

 the pith. 



Heart-shakes of both kinds usually occur at the base of a tree, 

 and are clearly seen on the stump left in the ground. They 



