ON THE DISEASE OF THE LARCH. 145 



those growing under unfavourable circumstances. Trees affected 

 with heart-rot, blister, those growing in a crowded state, and all 

 the other circumstances unfavourable to larch, favour the disease, 

 which I strongly suspect to be the effect rather than the cause. 

 Plants in nurseries are often affected with the C. laricis ; indeed, 

 the larch is seldom free from this pest, and, when grown year 

 after year in the same locality, and often transplanted in the same 

 soil, no wonder that the plantations suffer. Before planting out, 

 however, plants can be thoroughly cleansed by having all the 

 plants sheughed in as dry a state as possible, and not too tightly 

 packed. If the plants could be kept for a few days in the packing 

 shed, they would be all the better. Take of perchloride of mercury 

 1 lb., and dissolve in thirty gallons of tepid water, syringe the 

 plants with this solution, and when they are thoroughly dry 

 syringe again. This quantity is sufficient for about 20,000 to 

 30,000 plants ; the cure will be found to be complete, and its good 

 effect remains in the tree for a number of years. The perchloride 

 is a deadly poison, and should be handled with the utmost caution. 

 This solution must not in any case be applied to fruit trees, 

 as the poison might pass into the fruit. I am not of opinion 

 that it is practicable to use it in plantations. The only remedy 

 for them is to avoid all circumstances likely to favour the 

 attack. 



The larch, like all other forest trees, is more or less infested 

 with cryptogamous plants, and whether it is a disease or not is a 

 question of importance to arboriculturists. It is quite certain, 

 however, that trees thickly covered with lichen appear to have 

 lost their vigour, their foliage is scant, and in general presents a 

 very sickly appearance. But this appearance is not due directly 

 to the effects of the lichen. The lichen itself is produced by the 

 tree being either affected with some other disease or grown in a 

 crowded plantation, or on a heathy, peaty, ill-drained soil, or on 

 too severe an exposure. Under these conditions, the lichen will 

 insinuate itself and choke up the pores of the bark to the total 

 exclusion of the necessary light, air, and heat. The consequence 

 is, that the health of the tree, unless relieved, goes from bad to 

 worse, and eventually the tree dies. Till the lichen lay hold and 

 cover up the wood of trees from one to six years old, it has no 

 injurious effect ; but unless the tree is in a thriving state natiu'ally, 

 this it soon does with the results already stated. On the bark of 

 old trees, lichen has no bad effect whatever, as it is rugged, and 



