572 -^Causes of Disease in the Larch. 



the sap-wood of former years; and in converting part of that into 

 heart-wood; and in giving increased solidity to the heart- wood 

 previously formed." Now, if, by over-vigorous or too rapid and 

 unnatural growth, that part of the true sap, or blood, of the plant 

 destined to give additional solidity to previous formations should 

 be diverted from its appointed purpose, or if the annual deposit 

 for the first ten or fifteen years should exceed, say, one third of 

 the subsequent deposits, a diminished quantity of true sap natu- 

 rally follows ; and, with that, a diminution of that part of this 

 fluid which is appointed to consolidate the previously formed 

 heart-wood. If this view of the matter be correct, the inference 

 is, that the destruction of the heart-wood is attributable to the 

 too vigorous or rapid growth of the tree. 



I have also pointed out the practice of over-crowding of our 

 plantations, as one productive of baneful effects on the health of 

 the trees ; and I am really of opinion, so far as it regards this 

 practice with larch, that it is, perhaps, more hurtful to it than 

 planters may at first suppose. Nature, in her government of the 

 animal and vegetable kingdoms, has assigned to every species its 

 particular situation ; and it may be, and, no doubt, is, true, that 

 the proper food for bringing the larch to maturity is less plen- 

 tiful in this country than in that of which it is a native. How 

 improper, then, is the prevailing custom (and, I may say, gene- 

 ral rule) of crowding an acre with 4000 plants, whatever may be 

 the quality of the soil ? What should we think of a grazier who 

 would put 4000 cattle into fields barely sufficient to keep half or 

 a third of that number ? Should we not conclude that he knew 

 nothing of his profession? The cases are exactly similar; only 

 the effects are not so soon visible in the one instance as they are 

 in the other. Some may think this argument far-fetched and 

 overstrained; but take it in connexion with already established 

 facts, and it will not, by any means, appear so. The whole of 

 what are termed the original larches, which were planted out 

 solitarily, in pairs, or in groups, or such as were dispersed over the 

 ground at the rate of from twenty-five to fifty plants per acre, are 

 living evidences of the advantages of thin planting, or, what is 

 tantamount thereto, judicious and timely thinning. In fact, since 

 I have begun to study this subject more closely, it has become a 

 question with me, whether we should continue keeping plant- 

 ations with the trees thinned out to regular distances, which 

 certainly has the effect of preventing all the interior of the forest 

 from receiving a due proportion of atmospheric influence; or 

 whether, in the case of an extensive plantation, we should not 

 rather throw it all into groups of from fifty to a hundred trees 

 each, and cause it to be intersected with avenues from every 

 point. A free current of air would thus be admitted to the very 

 core ; the intersecting glades would afford excellent shelter and 

 winter pasturage for cattle ; and, the trees being completely open 



