1 66 THE NEW FORESTRY. 



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 approach- 

 ing 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 

 few species of similar habit, is our mixed woods. The species 

 planted are so numerous, and these of such wide disparity of 

 habit, that any forester might well be puzzled what to do in 

 thinning, where a portion of all the species had to be retained. 

 Indiscriminate mixture is one of the worst faults of forestry 

 in this country. We shall here, however, try to point out what 

 course the forester should choose under such circumstances. 



Age has really very little to do with the matter, and no 

 safe rule can be laid down on that line. Situation and expo- 

 sure makes so much difference to the growth of the trees that 

 it is quite a common thing, even on the same estate, to see 

 plantations of the same age differing so widely in height and 

 density that one might suppose there were years of difference 

 in their ages. The height and condition of the trees should 

 be the thinner's guide. Supposing that we have to deal with 

 a plantation of any kind in which the trees were originally 

 planted three or four feet apart, no thinning should be needed 



