4 OF WOOD IN GENERAL 



Dicotyledons are commonly slower of growth than conifers,^ and 

 their wood, especially that near the centre of the stem, is often 

 much harder. They bear as a rule also broad, net- veined leaves ; 

 and are known familiarly, therefore, as " hardwoods,^'' or as 

 " broad-leaved trees.^^ Such are the Oak, Beech, Ash, Elm, Teak, 

 Willow, Alder, etc. 



It is then only with the two classes of exogenous stems, those 

 of gymnosperms or needle-leaved trees, and those of dicotyledons 

 or broad-leaved trees, that we are concerned. 



Though, as we have already said, conifers and broad-leaved 

 trees present important differences in the structure and conse- 

 quent character of their wood, their manner of growth is so 

 nearly identical in its initial stages and broad outhnes that 

 we may well treat them at first collectively. It is, perhaps, 

 the many branches and the numerous small leaves exposed by 



Fig. 1. — Transverse section of an Oak, 25 years old. (After Le Maout and Decaisne, 

 from The Elements of Botany, by permission of Mr. Francis Darwin and the Syndicate 

 of the Cambridge University Press.) 



means of these branches to a maximum of air and light in 

 these two groups of plants (as contrasted with the general 

 absence of branching, and the small number and large size of 

 the leaves in ferns and palms) that has determined the produc- 

 tion of the progressively enlarging, solid stem that characterizes 

 them. It must be remembered, however, that the stem of a 

 tree fulfils several very distinct physiological purposes. Besides 

 bearing up the weight of leaves and flowers so as best to obtain 

 the air and light they require, it is the means of communication 

 between the root and the leaves. Through it the water and its 



^ ' ' This statement is too general when the trees of the whole world are taken 

 into account. Species of Eucalyptus and Casuarina, Altingia excelsa, Bo7}ibax incda- 

 haricum^ Gedrela Toona, Mahogany, and planted Teak grow faster than any Conifer. 

 Even among our European trees, Birch, Alder, Ash, and Sycamore more than hold 

 their own with Conifers for the first thirty years ; the rapid growth of Poplars is 

 well known, and Beech beats Spruce and Silver fir up to sev^enty or eighty years, 

 and after ninety outgrows Scots Pine." — Gardeners' Chronicle^ December 20, 1902. 



