STEMS AND BRANCHES 13 



these are the silver grain ; they are called by the botanist 

 medullary rays. 



The central portion of the wood of many large stems is 

 darker in color than the rest. This darker portion is dead 

 wood, and is called heart-wood ; the outer portion, called 

 sap-wood, is used in carrying the sap during the growing 

 season. The heart- wood of the Walnut-tree is very dark 

 brown; that of the Cherry, light red; and that of the 

 Holly, white and ivory-like. The heart-wood is the valu- 

 able part for lumber. 



If examined under a magnifying glass, the annual layers 

 will be seen to consist of minute tubes or cells. In most 

 trees these tubes are much larger in the portion that grew 

 early in the season, while the wood seems almost solid 

 near the close of the annual layer; this is especially true 

 in the Ashes and the Chestnut ; some trees, however, show 

 but little change in the size of the cells, the Beech being 

 a good example. In a cross- section, the age of such trees 

 as the Chestnut can readily be estimated, while in the 

 Beech it is quite difficult to do this. Boxwood, changing 

 least in the character of its structure, is the one always 

 used for first-grade wood-engravings. 



When wood is cut in the direction of the silver grain, 

 or cut " quartering" as it is called by the lumbermen, the 

 surface shows this cellular material spread out in strange 

 blotches characteristic of the different kinds of wood. 

 Fig. 16 shows an Oak where the blotches of medullary 

 rays are large. In the Beech the blotches are smaller; 

 in the Elm quite small. Lumber cut carefully in this 

 way is said to be " quartered," and with most species its 

 beauty is thereby much increased. 



Any one who studies the matter carefully can become 

 acquainted with all the useful and ornamental woods 

 used in a region; the differences in the color of the heart- 

 wood, the character of the annual layers, and the size and 

 the distribution of the medullary rays, afford enough 

 peculiarities to distinguish any one from all others. 



