FIR PLANTATIONS. 137 



plantations are composed entirely of one tribe or 

 family of trees ; that is, if a plantation be composed 

 entirely of the different sorts of firs, the gases 

 arising from the decomposition of their own kind is 

 injurious to their health, whereas the gases arising 

 from the decomposition of firs are favourable to 

 the health of hard-wood trees. And again, the 

 gases arising from the natural decomposition of 

 hard-wood trees are injurious to the living plant in 

 the neighbourhood, but the same gases prove bene- 

 ficial to the health of fir trees. The reason of this I 

 do not pretend to explain, as a question of chemis- 

 try is involved in the answer ; still, from my own 

 observation, I am satisfied of the truth of what I 

 here assert, although I do not remember of ever 

 having heard that any other forester had ob- 

 served this phenomenon : and it is to be regretted 

 that, generally speaking, foresters are not allowed 

 time and expenses to keep young plantations in 

 the clean healthy state which their ultimate value 

 demands. I have observed, in several places of 

 note in Scotland, where men of first-rate abilities 

 acted as foresters, that the plantations under their 

 charge, although generally well conducted in other 

 points, were, notwithstanding, always in a confused 

 state from the prunings of all felled trees lying 

 upon the ground ; and upon inquiry into the reason 

 of such a state of things, I have always learned 

 that, the operation of keeping plantations clean 



