2 9 2 ENGLISH ESTATE FORESTRY 



attack than elsewhere; (7) trees in mixed woods are less 

 liable to attack than those in pure ones; (8) the larch 

 aphis interferes with the transpiration of water by the 

 leaves, which favours the spread of the fungus ; (9) although 

 the disease is not hereditary, it is prudent to avoid collecting 

 seed from trees which have actually contracted disease ; 

 (10) it is possible that the disease occurs in nurseries, 

 and may be transmitted to plantations at the time of 

 planting out; (11) home-grown seed is preferred to foreign; 

 (12) self-sown larches appear more immune from attack 

 than planted ones; (13) when once the disease has obtained 

 a footing on a tree, a return to a healthy condition cannot 

 be looked for. 



In 1902 the eminent mycologist, Dr. Massie of Kew, 

 published in the Journal of the Board of Agriculture the 

 results of experiments on the larch disease, more particularly 

 in reference to its method of infection. Dr. Massie's chief 

 conclusions were that the fungus was a genuine wound 

 parasite, thus agreeing with Hartig and Marshall Ward, and 

 that the majority of the wounds through which it entered 

 were the work of the larch aphis. He believed that, if the 

 latter could be got rid of, the larch disease would eventually 

 disappear. 



The above paragraphs give a few of the more important 

 opinions held and facts noticed in connection with the 

 observance of this pest. To digest all that has been written 

 on the subject from time to time would require a book to itself, 

 and not very much more definite information than that 

 given above would be obtained from it. All scientific in- 

 vestigators have endeavoured, to a greater or less degree, 

 to discover the conditions under which the fungus spores 

 penetrate the tissues of the bark, and obtain a footing on the 

 branch or stem. To say that they can only enter by means 

 of wounds does not help us much, or satisfactorily explain 

 all cases of severe attack. 



The first thing to decide is the definition of such a 

 wound. If it means any injury to the stem by which the 

 bark is removed or broken, then we can point to hundreds 

 of such wounds which show no trace of infection, although 

 they exist within a few inches of undoubted blisters. On 



