276 THE STRUCTURB OP TIMBER. 



the roots as of the stein, for the former can no more increase in 

 thickness in the case of a tree that has heen ringed, than can 

 the stem below the point of rupture of the bark. 



Having thus briefly sketched the manner in which wood is 

 formed, let us look a little more closely at its structure, especi- 

 ally where this may be made the means of enabling us with ease 

 to identify the timber produced by some of the commoner genera 

 of forest trees. 



When examined under the microscope many timbers may be 

 identified readily by the characteristic markings or sculpturings 

 that are met with on the cell walls; but one of the objects of 

 this paper is to call attention to certain peculiarities that are 

 sufficient in many cases to decide the kind of timber without 

 having recourse to the microscope. A pocket lens is a useful 

 aid in this work, but still nothing more than good eyesight is 

 absolutely necessary. 



Nearly all timber is the produce of the growth of trees belong- 

 ing to two great divisions of the vegetable kingdom, the conifers 

 and the dicotyledons. The former term is now freely used in 

 popular language, while the latter includes the trees that are 

 commonly called hardwoods, or deciduous, or broad-leaved trees. 

 It is immaterial which term we make use of so long as we under- 

 stand exactly vt^hat we mean, but "deciduous" cannot be correctly 

 used as opposed to conifer, because certain conifers, notably the 

 larch, are also deciduous, and many trees that would, under 

 this loose system of nomenclature, be included in the deciduous 

 group, do not annually shed their leaves, as, for instance, the 

 holly and evergreen oak. The ''hardwoods," too, do not all 

 furnish wood that is hard, and the wood of certain conifers is 

 much harder than that of many trees that bear the name. It is 

 a better division of arboreal vegetation to arrange trees into two 

 groups according to the prevailing form of the leaves ; the one, 

 ** needle-leaved" trees, corresponding to the conifers, and the 

 other, "broad-leaved" trees, corresponding to the dicotyledons. 



A piece of timber yielded by a conifer can at once be distin- 

 guished from that of a dicotyledon by the fact that it contains no 

 vessels, if we except a few in tlic immediate neighbourhood of 



