THE DISEASES OF CONIFERS, 



129 



Obviously young Pines in beds should not be exposed to 

 powerful insolation at a time when their roots are in hard 

 frozen soil as above described, and in those cases where such 

 dangers are imminent a piece of gauze or other shelter will 

 reduce the chances of disaster. 



Equally obvious is it that suitable drainage operations may 

 make all the difference to a locality not quite fitted for growing 

 such plants, and I want to take this opportunity of insisting 

 upon the very important fact — which applies to other plants as 

 well as Conifers — that the operation of drainage does not 

 consist in merely removing superfluous moisture ; far" more 

 important is the pressing into the interstices of the drained soil 

 of atmospheric oxygen, which does so much work of various 

 kinds in the labyrinth of passages which it traverses, that a whole 

 lecture would not nearly exhaust the treatment of this subject 

 alone. Another extremely pertinent point in this connection is 

 that the drained soil can be warmed by the sun's rays, or by the 

 higher temperature of the air referred to, not only more easily, 

 but also more equably. 



Other advantages of suitable draining are too well known to 

 be dwelt upon. The dangers of improper or over-draining do 

 not immediately belong to my present subject, but obviously they 

 must be guarded against. 



Passing now to the diseases due to unsuitable conditions 

 in the sub-aerial and atmospheric environment, the following 

 points may be considered. 



Pines, especially when the foliage is young, and still more 

 particularly when the plants themselves are young, are apt to 

 lose many leaves, and even to be killed, by undue chilling of 

 the surfaces, cold dry winds being perhaps the most fatal agents 

 in this country. I have already referred to that form of leaf- 

 casting which is caused by this ; but it is perhaps commoner 

 to see parts of the tree only, in the case of the more tender 

 Pines, with their foliage brown and shrivelled, than to have a 

 general fall of the leaves. 



A curious class of diseases, not common in the Pines, 

 perhaps, but stated as occurring in P. Strohus and some others 

 with thin cortex, are the various kinds of "rifts" — i.e., more 

 or less vertical fissures, which extend up and down the exposed 

 trunks pf trees facing the south-^esji, The particular kind of 



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