IDENTIFICATIOlSr OT TEUE MAHOGAISTY. 17 



apple, pear, and quince belong to one family, and walnut and hick- 

 ory to another family. 



Fibers. — The comparatively long thin cells usually comprising the 

 bulk of the wood, but too small to be seen except with a high-powered 

 microscope. Distinguished from the pores in the hardwoods, which 

 are larger but less numerous. 



Growth rings. — The well-defined layers of wood put on each season 

 usually, but not necessarily, limited to one each year. 



GuTTi. — A white or dark deposit, partly or wholly filling the sap 

 pores or the gum ducts of certain woods. 



Interlocked grain. — Fibers slanting around the tree in one direction 

 for a number of years and then reversing to the other direction, and 

 later reversing again, and so on, producing a " ribbon " effect on 

 quarter-sawed lumber. 



Light-colored lines. — Very thin light-colored lines extending cir- 

 cumferentially on the cross-section. These may mark the end of 

 each growth ring, or many may be formed each season, as in sapeli 

 and " Colombian mahogany." Composed of soft tissue technically 

 known as parenchyma. 



Longitudinal surfaces. — Either radial or tangential surfaces, as 

 distinguished from cross-section, or end grain. 



Pores. — Larger cells with open ends set one above the other, and 

 used for conducting sap, as distinguished from the smaller wood 

 fibers with closed ends used to give strength to the tree trunk. (True 

 pores are not found in the coniferous woods, in which the fibers serve 

 the combined purpose of conducting sap and giving strength to the 

 tree.) 



Radial. — Along the radius. 



Radial surface. — A longitudinal surface cut approximately along 

 the radius of the log, that is, from the bark toward the center ; equiv- 

 alent of edge grain or quarter-sawed surface. 



Rays. — Eows of cells extending horizontally in a tree from the 

 bank inwardly at right angles to the grain. Visible on strictly 

 radial surfaces of all woods; very conspicuous in quartered oak. 

 (See fig. 13.) On end surfaces they may be seen with a lens, or 

 occasionally without, as fine radial lines crossing the growth rings. 



Ring-porous. — Having the pores at the beginning of each growth 

 ring comparatively large, with more or less abrupt decrease in size 

 toward the outer portion of the growth ring. 



Ripple marhs. — Fine transverse markings uniformly spaced on 

 the tangential faces of wood. (See fig. 12.) 



Soft tissue. — Thin-walled cells, often in rows, usually producing 

 lighter-colored lines when cut across the grain, used to store food. 

 Technically called parenchyma. 

 79793°— 22 2 



