IDENTIFICATION OF TRUE MAHOGANY. 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. 
Gum. — 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 marks. — 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 
