122 I'KKLIMINAKV WoUKS. 



As a rule in .sylvicultnre a change of species is culleil for 

 only ill special cases, such as the following :— 



(1.) "When the original species has, on general grounds, 



been found unsuited for the locality. 

 (2.) When an inferior species is to be replaced l)y a more 



valuable one. 

 (3.) "When the fertility of the soil, in consequence of faulty 



treatment, heavy removal of litter, etc., has deteriorated, 



so that the original species will no longer thrive on it, 



and must give way to one less exacting. 

 (4.) When a temporary shelter- wood (nurses) is required for 



a tender species. 

 (5.) When the object is to extend the growth of one species 



uniforml}' over a certain area. 



Section II. — Fencing. 



Fencing is used for nurseries and woods. Whether it is 

 required for the latter depends on the extent to which a 

 particular species is exposed to attacks by cattle or game. 

 Erecting fences is ordinarily one of the heaviest items of 

 expense in the formation of woods, and it is essential to select 

 ill each case that kind which, while meeting the necessary 

 requirements, involves a minimum outlay. 



The number of different kinds of fences which are in use or 

 have been suggested is very great. It is not intended to 

 describe these here in detail, as a practical knowledge can 

 only be obtained out of doors. It will suffice to enumerate the 

 principal kinds, and to give illustrations of a few which seem 

 specially adapted for sylvicultural purposes.* 



1. llrdiics. 

 Hedges are formed of a great variety of trees and shrubs, of 

 which, for temperate Europe, the following may be mentioned : 

 Hawthorn, blackthorn, beech, furze, holly, laurel, yew, box, 



A <k'taile<l account of feiicos will ln' luiiinl in • Tiir l^'incMci." hy .lainc^ 

 liiown. oth edition, pages ys — 17U. 



