SPECIMEN PAGE 
298 ENGLISH ESTATE FORESTRY 
is the most likely explanation of the most puzzling problem 
of the forestry world. 
It may be stated at the outset that the life-history of 
the fungus, as given by Hartig, Marshall Wood, Massie, and 
others, has less connection with the practical side of the 
problem than many suppose. Tor all practical purposes, the 
life-history of the fungus may be generally accepted as 
following the same course on every soil, and in all parts of 
the country. 
The problem for solution is the cause of the great 
difference in the degree with which one plantation, or one 
part of a plantation, is affected, as compared with another. 
The disease is practically universal. Why, then, should 
its virulence differ to the extent that it does ? Without 
pretending to solve this problem off-hand, it may be worth 
while discussing a few sides of the question which seem 
most pertinent to it, and which may throw stronger light 
on those points which have not hitherto received the full 
attention that they deserve. 
The first thing to settle, in our opinion, is the real 
nature or significance of the disease in the life-history 
of the host. Is it a cause of bad health or the effect 
of it ? Nine out of every ten foresters, and ten out of 
every ten scientists, would probably say the former. Yet 
we do not hesitate to question the accuracy of this opinion. 
To explain our meaning quite clearly, it is necessary to 
examine the somewhat ambiguous statement that a perfectly 
healthy larch may be diseased. Most practical foresters 
know that the great majority of thriving larch trees carry 
blisters caused by Pezizi Wilkommi, and that these blis¬ 
ters can exist without affecting the growth or commercial 
value of the tree in the least. In such cases, therefore, 
it may be said that healthy trees can also be diseased. But 
when practical men speak of diseased plantations, they 
invariably refer to those cases where the growth of the 
tree is apparently affected, and its market value is undoubt¬ 
edly decreased by the presence of numerous blisters which 
occur on stem and branches, and which cripple and deform 
its entire habit of growth. As both of the above-cited 
examples of blister attack may exist side by side, or within 
