18 



TIMBER. 



removal of the bark from a fresh piece of white pine, cut in winter, where 

 they appear as conspicuous white lines, extending often for many inches 



up and down the stem. 



Neither the horizontal nor the vertical resin 

 ducts are vessels or cells, but are openings 

 between cells, i. e., intercellular spaces, in 

 which the resin accumulates, freely oozing out 

 when the ducts of a fresh piece of sapwood are 

 cut. They are present only in our coniferous 

 woods, and even here they are restricted to 

 pine, spruce, and larch, and are normally ab- 

 sent in fir, cedar, cypress, and yew. 



Altogether the structure of coniferous wood 

 is very simple and regular, the bulk being made 

 up of the small fibers called tracheids, the dis- 

 turbing elements of pith rays and resin ducts 

 being insignificant, and hence the great uniform- 

 ity and great technical value of coniferous wood. 



Fig. 6.-Block of oak. C. S., 

 cross section ; R. S., radial sec- 

 tion ; T. 8., tangential section ; 

 m. r., medullary or pith ray ; a, 

 height, b, width, and e, length 

 of a pith ray. 



"WOOD OF BROAD-LEAVED TREES. 



On a cross section of oak, the same arrangement of pith and bark, 

 of sapwood and heartwood, 





mmm 



m 



¥ m\\\ 



1 ii PA 



and the same disposition of 

 the wood in well-defined con- 

 centric or annual rings occurs, 

 but the rings are marked by 

 lines, or rows, of conspicuous 

 pores or openings which oc- 

 cupy the greater part of the 

 spring wood of each ring (see 

 fig. 6, also fig. 8) and are, in 

 fact, the hollows of vessels 

 through which the cut has 

 been made. On the radial sec- 

 tion, or quarter-sawed board, 

 the several layers appear as 

 so many parallel stripes (see 

 fig. 7); on the tangential 

 section or "bastard" face, 

 patterns similar to those men- 

 tioned for pine wood are ob- 

 served. But while the pat- 

 terns in hard pine are marked 

 by the darker summer wood 

 and are composed of plain, 

 alternating stripes of darker 

 and lighter wood, the figures 

 in oak (and other broad-leaved woods) are due chiefly to the vessels, 



I ffl 1 1 



™)!w Will 







wm\m fmi 



Mi 



V .OF, 



MM 







Fig. 7.— Board of oak. CS, cross section; RS, radial sec- 

 tion; TS, tangential section; v, vessels or pores, cut 

 through; A, slight curve in log which appears in sec- 

 tion as an islet. 



