142 ON THE DISEASE OP THE LARCH. 



the level of, and 9 miles distant from, the sea, and on the north 

 side of a steep hill, freely exposed to the prevailing winds. About 

 15 acres, some of which grew on arable and some on uncultivated 

 soil, was the first examined. 



The soil was of a thin, yellow, hazel, loamy description, resting 

 on a hard subsoil of granitic till, so hard that a pick could not be 

 forced into it without the greatest difficulty. I found this por- 

 tion in a very diseased state with heart-rot, blister, and aphis. In 

 one spot, about the centre of the piece, referred to, were a number 

 of large trees in a thriving state, which on examination I found 

 to be growing in loose deep soil formed by the filling up of large 

 pits with weeds and earth, through which the roots penetrated for 

 a distance of about 5 feet. 



Each of the trees growing here had a few blisters, but none 

 showed the least trace of heart-rot. The rest of the plantation was 

 from seventy to eighty years old, and grew on different varieties 

 of soil, but had the same elevation and exposure as the younger 

 part. Where the soil was thin and the subsoil hard, almost all the 

 trees were diseased ; but where the soil was deep, and the subsoil 

 loose and free from large stones, no disease was seen. One very 

 large tree was found in a very diseased state when cut away from 

 the root. The soil on which it grew was of a light loamy nature, 

 and about 4 feet deep. On grubbing up the root a large boulder 

 of rough granite was found directly under and in contact with the 

 diseased side of the tree. 



There is also good reason for supposing that soil previously 

 occupied with Scotch fir tends to produce heart-rot in larch, because 

 the subsoil is often very hard, much more so than if it had not 

 been planted. The disease in this case is more disastrous than 

 in any other, as the fungi on the old roots attack the roots 

 of the larch on receiving the least injury. Consequently it is ob- 

 served much earlier and on a larger scale than if planted on virgin 

 soil of the same quality. 



The only means at our disposal to prevent this disease are to plant 

 the tree in such places, where not only the soil but also the situa- 

 tion and exposure are suitable to its nature. The best soils for 

 growing larch are those formed by the debris of rocks and alluvial 

 soils on the banks of rivers. Deep, sandy, loamy soils are all good 

 for rearing larch, provided there is no stagnant water about the 

 roots. Nevertheless it grows and thrives well though the roots are 

 continually many feet under water, if not stagnant. For instance, 



