42 Mr. Arthur Deane on 



THE TIMBER. 



Commercially, timbers are divided into softwoods" and 

 "hardwoods," but this does not, by any means, represent a 

 scientific classification. Foresters also roughly divide trees into 

 needle-leaved trees (or Conifers) and broad-leaved trees. To 

 the former belong the softwoods of commerce — Pines, Firs, and 

 Larches, while the broad-leaved trees include the hardwoods — 

 Oaks, Elms, and Chestnuts, although some timbers in the latter 

 group might be described as softwood, such as the Poplar, 

 Willow, Lime, and Horsechestuut. 



Length and Diameter Gkowth. 

 Once formed wood never lengthens, and a trunk or 

 shoot grows in length, only at its extremity, by means of a 

 bud, and then only during the growing season in which it is 

 formed ; but a trunk or shoot increases in girth by the annual 

 increment of a cylinder or wood, or to be more accurate, by the 

 addition of a hollow cone which is deposited on top of that 

 produced in the previous year to form a compact mass, appearing 

 on the cross cut end as rings. A nail or a spike driven into a 

 trunk used as a fence post will never be higher up, but such 

 objects will in time become covered by the increased diameter 

 due to the additional layers of wood. 



Parts of the Trunk. 



Cambium. — This is a generative layer and is situated between 

 the outermost or youngest layer of wood and the living bark {bast). 

 It is not only important in forming the new rings of wood after 

 the first year, but it also plays a prominent part in the occlusion 

 of wounds, and the success of grafting depends largely upon the 

 joining of the cambium of the scion to the cambium of the stock. 



The Cambium is a delicate, juicy, film-like sheet or mantle 

 which covers the root, trunk, branches and twigs like a huge 

 glove. It consists of thin Availed cells, densely filled with 

 protoplasm and large nuclei, and divides up to form not only new 



