18 THE STEUGGLE FOS EXISTENCE. 



■vigorous, and, therefore, more promising individuals ; and so on. 



However great the care or skill exercised in felling, conversion 

 and export operations, a certain amount of damage to the standing 

 plants cannot be avoided. The smaller and weaker individuals will 

 of course, on the whole, suffer most, but the fall of a heavy tree is 

 niore Hkely to break and throw back for ever the larger or more 

 vigorous plants possessing a rigid, more or less unyielding stem 

 than the weaker and therefore more flexible individuals. 



(g) Climbers. — CKmbers kijl or at least unfjt trees for the strug= 

 gle for existence in six different ways-^ 



(i) They may strangle the stems of their supports, narrowing 

 year after year the channel through which alone the sap, 

 taken up from the soil, can ascend. If the tree attacked 

 forms a heartwood, it must ultimately die of sheer starva- 

 tion, 

 (ii) As the climber and its victim grow in diameter, the increas- 

 ing pressure on the bark of the latter necessarily forces the 

 elaborated sap to descend obliquely and spirally instead of 

 vertically, and thus gradually diminishes the amount of nour- 

 ishment conveyed to the xmder portion of the tree. The roots 

 thereby suffer most, and their consequent debilitation and 

 contraction obviously reacts with increasing effect on the 

 crown above, 

 (iii) Climbers also bend down by their sheer weight the stems 



and branches of their victims, 

 (iv) When they get up into the crowns of their supports, they 

 invade and overspread those crowns, which cannot, therefore, 

 hear fjheir full quantum of fohage, and are also thereby im- 

 peded both in their lateral and upward development, espe- 

 cially in the latter, 

 (v) They distort the boles of their supports, and thus necessi, 



tate the removal of these latter by the forester, 

 (vi) When the same climber attacks two trees, the fall of one of 

 these might bring down the other or at least severely strain 

 it. 

 These various injuries will of course be greater in propoi-tion to 

 the weakness and low stature of the individual attacked and the size 

 and weight of the chmber. 



IV. GOJIPLETEXESS OF THE LEAF-CANOPT.^It is ohvioUS that 



those individuals, whatever their age and size maybe, which have 

 free space around and over them, will have every chance ofgrovdng 

 PA aud surviving, while others, taller and stronger than they, but 



