70 CHARACTKH AND COMPOSITION OF WOODS. 



The litness of a s[)ecies to l)t' laisfd in piiie woods depeiuls 

 on its capacity to preserve, or even improve, the factors of 

 the locality, in other words, whether the species preserves a 

 complete leaf canopy to an advanced age, and secures the 

 accumulation of a sutticient layer of humus. As indicated 

 in section IV. of chapter I., beech, silver tir and spruce act 

 most beneficially in this respect, and next to these some of 

 the pines. Apart from them, several others are frequently 

 grown in pure woods, such as oak. larch, Scotch pine, birch, 

 and willows, on account of their great utility. 



Of the remaining, or so-called dcpnuh itt species, few are 

 found in pure woods, and then only under special circum- 

 stances ; for instance, hornbeam replaces beech in frost 

 localities, Cembran pine and mountain pine occur at high 

 elevations, maritime pine on dunes near the seashore, alder 

 in wet localities, sweet chestnut as coppice for pit wood, vine 

 stakes, etc. On the whole it may be said, that dependent 

 species may be grown as pure Avoods in the following 

 cases : — 



(l.^i If the factors of the locality are such that an imperfect 

 cover and want of humus do not materially injure them ; as 

 in deep fertile soils, which enjoy an ample and well distri- 

 buted rainfall, or which are kept moist by ground water or 

 irrigation. 



(2.) If the woods are treated under a short rotation, so that 

 they are cut over before any excessive interruption of the leaf 

 canopy has set in ; or if it is intended to underplant them, 

 when the}' connnence to open out, as in the case of oak, larch, 

 and Scotch i)ine. 



(8.) If the object is to utilise localities which are only lit for 

 certain species ; for instance, alder and willow on wet soils, 

 hornbeam in frost localities, etc. 



(4.) If only one species linds a ready market, or is reciuired 

 for a ^|icciiil [)iM'[)ose. 



I'i.xcept in such cases, all ilej)eiuU:iil species should he I'aised 

 in mixed woods. 



