2 INTRODUCTION 



the soil many trees seem to be materially assisted 

 by the presence of the " spawn " or mycelium of 

 fungi, a mass of delicate threads investing their 

 roots, known technically as a onycorrMza. Ruskin 

 in his " Modern Painters " emphasises the dependence 

 of tree-growth upon the leaves, pointing out that 

 the size of every twig or branch is directly propor- 

 tional to the leaves that it bears. 



The main physiological function of wood is the 

 mechanical one of giving strength to the stem, to 

 enable it to resist its own increasing weight as it 

 grows in height and branches. 



The highest sub-kingdom of the plant world, the 

 seed-bearing or flowering plants, the Spermatophijta 

 or Phanerogamfia of botanists, among which only is 

 ■wood for all practical purposes produced, is sub- 

 divided into : (1) the Gymnospervi'ce, or plants the 

 seeds of which are naked, i.e. not enclosed in a fruit ; 

 and (2) the Angiosperm'ce, or fruit-bearing plants. 

 Of these, the Gymnosperms are all perennial trees 

 and shrubs, their only representatives in the Northern 

 Hemisphere being the Natural Order Coniferce, so 

 named from the general arrangement of its seeds on 

 a series of overlapping scales arranged in a cone. 

 The members, of this Order, which includes the Pines, 

 Firs, Cedars, etc., produce numerous narrow, rigid, 

 undivided leaves, whence they get the familiar name 

 of needle-leaved trees: they have much-branched 

 stems; and their wood is of rapid growth, soft and 

 of even texture, formed in annual rings of growth, 

 and generally resinous. They are, therefore, often 

 spoken of as " soft woods " or as " resinous woods," 



