256 



INDUSTRIAL PLANTS 



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I'iG. 235. — Transverse section of white oak 

 wood, ?. (Hartig.) 



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Fig. 236. — Transverse section of elm wood, I. 

 (Hartig.) 



Fig. 237. — Transverse section of ash wood, !. 

 (Hartig.) 



Fig. 238. — Transverse section of walnut 

 wood, 1. (Hartig.) 



planks, and is quite un- 

 suited for most of thie 

 uses of ordinary Avood. 

 Like bamboo, the hard 

 shell of the coconut, 

 and other materials 

 sharing some of the es- 

 sential properties of or- 

 dinary wood but differ- 

 ing from it decidedly in 

 structure, the palm- 

 trunk can scarcely be 

 regarded as a true wood 

 at all. Such materials 

 are best called pseudo- 

 woods, t o distinguish 

 them from true woods 

 which are always 

 formed by a cambium 

 layer. 



73. True woods. 

 The following include 

 the more important 

 woods commonly used 

 in this country: — 



Oak (Figs. ^235, 242, 

 243) is used extensively 

 for heavy construction 

 in common carpentry 

 and shipbuilding, and 

 in car and wagon work 

 on account of its ex- 

 traordinary strength; 

 also in the manufacture 

 of farm implements and 

 parts of machinery be- 

 cause of its hardness 

 and toughness, while its 

 unusual durability 



