THE NEW FORESTRY. 155 



adopted when the first crop has from any cause become thin. 

 Even-aged woods are most common, and final clear cutting 

 the rule. In British woods, however, a second, or even a third 

 crop of trees or poles might often be secured, if crops from old 

 stools were taken care of and thinned and regulated instead 

 of being left to produce what is little better than brushwood. 



SECTION II. — THINNING BRITISH WOODS AND PLANTATIONS 

 ON THE CONTINENTAL PRINCIPLE. AGE AND SIZE. 



In this we shall first endeavour to explain to the forester 

 or his man how to carry out the rules to be observed in 

 thinning on the above principle. From what has been said 

 before he will understand, it is hoped, that, the object of 

 thinning is not to give every tree in the plantation a clear 

 space to itself, or to admit the light and air down to the ground 

 round every tree, but (after thinning, at any stage,) to leave 

 the trees so judiciously crowded together that their lower 

 branches will meet and interlace so closely as to shut out the 

 light and air from above and cause them to die off and be shed 

 naturally at an early stage ; the process to be continued until 

 the plantation has reached maturity. At the same time, on 

 every tree a leader and head of live branches of sufficient size 

 to sustain vitality and promote healthy growth must be pre- 

 served. These are the main points to be kept in view, viz., 

 the early and continuous decay of the lower branches as the 

 top-growth progresses, and the preservation of a healthy 

 growing top. This is " density," and it must not be forgotten 

 that those conditions must be maintained from beginning to 

 end. Once dense always dense. According to Hartig, trees 

 " that are reared in a very dense wood and then suddenly 

 isolated in later life, suffer from sweating of the cortex," or 

 top-drought, are checked in growth, becoming bark-bound, 

 and finally stag-headed. This is very noticeable in the ash 

 when over-thinned, also in the larch, in which we have seen 

 the annual rings decrease greatly in width after a severe 

 thinning when- the trees had reached middle-age. These facts 

 must, therefore, be borne in mind when plantations approaching 

 maturity are thinned with a view to augmenting the annual 

 increment — a subject referred to elsewhere. 



A difficulty which the forester has to contend with in this 

 country, and one almost unknown on the Continent, where 

 pure forests are so extensive and mixtures restricted to a very 



