WOUNDS 249 



RING-WOUNDS 



These are often caused by game and mice, though they may 

 also be due to human agency, as, for instance, in a mixed wood, 

 where it is desirable to protect a valuable species against its 

 more vigorous neighbours. Their effects upon the tree are not 

 always alike. It is known that, if even a narrow band of cortex 

 be removed completely round the stem, the cambium below 

 the girdled portion ceases to be nourished, and there, as a 

 consequence, growth in thickness comes to a stand-still. As the 

 tree even where ringed retains its power of conducting the 

 ascending sap, it remains alive as a rule for some years. What 

 the conditions are that limit the duration of life of the portion 

 above the ring-wound has not yet been fully made out. 1 In June 

 1871 I selected fifteen equal-sized Scotch pines 120 years old 

 which were standing close together, and from these I completely 

 removed the cortex to the height of some six feet. While 

 certain of the trees died in 1872, several were still perfectly 

 healthy in 1 877. As this shows that it is not the desiccation ot 

 the exposed portion of the stem from the surface inwards that is 

 the sole cause of death, investigation should be directed to the 

 question whether the cessation of growth beneath the ring- 

 wound may not prejudicially affect the absorption of water by 

 the roots. 



Those cases where ringed trees remain alive for a long period 

 may possibly be explained by root-engrafting, the roots of the 

 girdled stem being thus nourished by neighbouring trees. 



PRUNING 2 



Although the pruning of trees is a subject that has often 

 been treated in forestry literature, still the views regarding its 

 admissibility are so diverse that a somewhat full discussion of 

 the operation may not be out of place here. 



The natural pruning of trees is accomplished by shade, which 

 causes the branches to become functionless, and ultimately to 



1 This is not the place to discuss bicollateral fibro-vascular bundles ; 

 where the plastic materials may descend in the bast organs near the pith. 



2 R. Hartig, Zersetzungserscheinungen, pp. 68 et seg. 



