208 Studies in Forestry [CHAP, ix. 



deducting the various outlays capitalized at compound interest 

 up to that date, would show a profit of 12 %. It is impossible 

 to criticize such a vague estimate without examining all the 

 data closely, and ascertaining what the results would be for 

 a fall of timber fixed at 100, 120, or 150 years; but, at any 

 rate, it is worth remarking that the practical effect of Alers' 

 agitation has been to induce the Prussian Government to 

 undertake regularly the removal of all dead branches in forests 

 grown for the production of valuable timber stems, and not 

 intended merely to be utilized as fuel. From the national- 

 economic point of view this may be advisable in State forests, 

 though for private landowners it is a purely financial question, 

 concerning which local experience will best guide the sylvicul- 

 turist to a sound judgement about the matter. In accordance 

 with the natural laws of tree-growth, as increment begins at the 

 top and is gradually continued towards the base, the removal 

 of a portion of the foliage diminishes the amount of elaborated 

 nourishment available for structural purposes towards the 

 butt-end of the trunk, and thus leads to improvement in the 

 form-factor of the bole ; whilst at the same time, as R. Hartig 

 has also shown, the quality of the timber produced improves 

 the more, the less difference there is in the quantitative incre- 

 ment proportionately to the surface of the foliage through 

 which the process of transpiration is carried on. That, in 

 consequence of this artificial thinning of the crown, the growth 

 in height is stimulated, is a point about which experts have 

 hitherto differed, and which has not yet been determined by 

 any series of authoritative experiments. 



Thus, while special circumstances have most influence in 

 each particular case relative to the remunerativeness of such 

 measures in private woodlands, the general statement can at 

 any rate be made, that the removal of sickly, rotting branches 

 or of all those infected with parasitic growth of Loranthus or 

 Mistletoe, or of such as exhibit deformities like twig-clusters 

 (e. g. those caused by Aeddium elatinum on Silver Fir, and 



