4:4 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



young trees also frequently occur near the surface of the ground, 

 being caused when lifting the plants from the nursery beds^ by 

 the feet or the tools of the men engaged in planting them, or by 

 rabbits, hares, voles, or other animals. As regards the base of a 

 young branch being a vulnerable point, it may be said that spores 

 are liable to collect and lodge in the upper angle of a branch; and 

 that a wound haa frequently been caused at that place through 

 the rupture of the bark, due to the branch bending down under 

 its own weight, or under the weight of an accumulation of snow, 

 or to its swaying during a heavy gale, or to a variety of other 

 circumstances. Hence the base of a branch is a vei-y weak point 

 where disease is concerned. 



5. Do any conditions of climate, soil, exposure, or situation 

 favour disease .? Low, humid situations, and damp, undrained 

 land, are factors predisposing to disease. 



6. Are trees less liable to attack in high, breezy situations than 

 in low, inuggy valleys ? The answer is in the affirmative, the 

 conditions at high elevations being unfavourable to the develop- 

 ment of the fungUM, and late and early frosts being much moie 

 frequent at low than at high elevations. 



7. Are trees less liable to attack in inixed woods than in pure 

 ones ? It cannot be said that mixing the larches with other trees 

 is a guarantee of complete immunity from the disease, but the 

 evidence was strongly in favour of a mixture securing compara- 

 tive freedom fiom attack. The spreading of the spores from one 

 larch tree to another is hindered by the surrounding trees of other 

 species; and when these latter are dense-crowned, the vitality and 

 rate of growth of the larches are enhanced. 



8. 7s there any connection between larch disease and the attack oj 

 insects such as the Larch A2)his ? Though the Aphis is not the 

 primary cause of the disease, it is probable that a tree infested 

 with Aphides is more likely to conti'act the disease than a perfectly 

 sound specimen. The Aphis interferes with the transpiration of 

 water by the leaves ; this tends to the accumulation of moisture in 

 the stem, and it thus favours the spread of the fungus. It is also 

 possiV)le that the Aphides predispose to disease by making wounds 

 in the epidermis of the shoots and foliar spurs, through which the 

 fungus may be able to gain an entrance. But the Aphis probably 

 assists the disease more in the former manner than in the latter. 



^ Also by drawing the young plants together in a bundle by means of a 

 green withe. — Hon. Ed. 



