48 Mr. Arthur Deane on 



Wood Rays. — An old Oak stump on the cross-cut surface 

 shows tliiii plates of variable length arranged i-adially (and 

 vertically) through the wood. Sometimes they are called pith or 

 medullary rays, two ^•cry inappropriate names, as they have no 

 relation whatever with the jiith or medulla, neither from the 

 historical nor evolutionary standpoint. They arise from the cambium 

 ring at irregular intervals during the gi'owth in thickness, 

 extending into the bast. 



No softwood or hardwood is devoid of wood rays, although 

 they differ considerably in size in different timbers, their number 

 and size influencing the technical properties of wood, and, in 

 some species, as in Oak, two sizes are found. In Hornbeam 

 and Alder the broad rays appear to be due to the crowding 

 together of the finer rays into bundles to form compound rays 

 or "false rays." Rays are more conspicuous in hardwoods than 

 in softwoods, while in the latter they are so fine and crowded 

 that they often give quite a silken gloss to planed timber. 



The physiological function of wood raj^s in the tree is to 

 convey the various food substances, and in winter they usually 

 act as storehouses for starch and other food substances, ready to 

 supply the cambium in the coming spring. In fact, the presence 

 or absence of reserve starch, in some trunks, under certain 

 conditions serves to determine when the tree was felled. 



Anatomy of Woods. 

 Wood may be composed of four different kinds of histo- 

 logical elements, although all of them are not necessarily present 

 in the wood of every species. They form the bricks, so to 

 speak, Av^hich build up the body of the tree, and those elements 

 that are present are always firmly cemented together, the qualities 

 depending in a large measure upon their character and arrange- 

 ment. One character of wood which strikes us at once is its 

 fibrous nature ; it is shown clearly by the splintery fracture 

 of a branch broken across the grain. The elements present in 

 >vood have a very definite arrangement, as everyone, who has 



