134 



VEGETABLE LIFE AND WORK. [SECTION 16, 



shown in Fig. 444, are only the fifteen-hundredth of an inch wide. Those 

 of Buttonwood (Fig. 447) are larger, and are here higlily magnified besides. 

 The figures show the way wood-cells are commonly put together, namely, 

 with their tapering ends overlapping each other, — spliced together, as it 

 were, — thus giving more strength and toughness. In hard wobds, such 

 as Hickory and Oak, the walls of these tubes are very thick, as well as 

 dense ; while in soft woods, such as White- Pine and Basswood, they are 

 thinner. 



411. Wood-cells in the bark are generally longer, finer, and tougher 

 than those of the proper wood, and appear more like fibres. For example. 

 Fig. 446 represents a cell of the wood of Basswood of average length, and 

 Fig. 444 one (aud part of another) of the fibrous bark, both drawn to the 

 same scale. As these long cells form the principal part of fibrous bark, or 

 bast, they are named Bast-cells or Bast-fibres. These give the great tough- 

 ness and fiexibility to the inuer bark of Basswood (i. e. Bast-wood) and of 

 Leatherwood; and they furnish the invaluable fibres of flax and hemp; 



the proper wood of their stems 



US 



\J 



449 



being tender, brittle, and de- 

 stroyed by the processes which 

 separate for use the tough and 

 slender bast-cells. In Leather- 

 wood (Dirca) the bast-ceUs are 

 remarkably slender. A view of 

 one, if magnified on the scale 

 of Fig. 444, would be a foot 

 and a half long. 

 412. The wood-cells of Pines, 

 and more or less of all other Coniferous trees, have on two of their sides 

 very peculiar disk-shaped markings (Fig. 448-450) by which that kind of 

 wood is recognizable. 



413. Ducts, also called Vessels, are mostly larger 

 than wood-cells : indeed, some of them, as in Bed Oak, 

 have calibre large enough to be discerned on a cross 

 section by the naked eye. They make the visible porosity 

 of such kinds of wood. This is particularly the case with 

 Dotted ducts (Fig. 451, 452), the surface of whicli 

 appears as if riddled vrith round or oval pores. Such 

 ducts are commonly made up of a row of large cells more 

 or less confluent into a tube. 



Sealariform ducts (Fig. 458, 459), common in Fcras, 

 and generally angled by mutual pressure iu the bundles. 



Fig. 448. Magnified bit of a pine-shaving, taken pafallel with the silver graia 

 449. Separate whole wood-cell, more magnified. 460. Same, still more magnified; 

 both sections represented : a, disks in section, 6, in face. 



Fig. 451, 452. A large and a smaller dotted duct from Grape- Vine. 



