124 HEART-ROT 



with the increment borer, and be prepared to clear fell as 

 soon as they reach a remunerative size. The poles can then 

 be sold for pit props, for which purpose a little heart-rot is 

 not a serious blemish. 



No means of artificially aerating the subsoil is economi- 

 cally possible. I have seen larch plantations on land that 

 was previously common, where the ground was said to have 

 been double-dug before planting. Heart-rot was not very 

 serious, but it was unmistakably present. Double-digging 

 will at most affect the top 16 in., and aeration must go down 

 much deeper than this in order to prevent pumping. Natural 

 aeration may, however, be encouraged by planting deep- 

 rooting trees such as oak or false acacia. In Germany, 

 lupin is also used on heaths for this purpose, and is allowed 

 to grow for a few years before planting trees. 



Destroying all fructifications will no doubt have a palliative 

 effect, especially in woods where Forties annosus is not yet 

 abundant. It removes, at any rate, one of the sources of 

 infection, and we know that spores are made in great 

 quantities where fructifications are allowed to appear. In 

 looking for them it should be remembered that they are 

 borne particularly on the trunks of dead conifers. They 

 are always formed near the base, and are often quite hidden 

 in the debris of leaves, twigs, and weeds that surround the 

 trunk. By treading lightly all round the tree' their presence 

 can often be discovered. 



The remains of rotted trees should be burnt whenever it 

 is possible, but grubbing up stumps is so expensive that 

 woods can seldom be effectively cleared in this way. In 

 some cases, however, such trouble will be well repaid. 

 There is one wood which I have kept under observation for 

 many years without ever finding Fames annosus. The wood 

 is a fairly large one, and in the last twenty years conifers 

 have been widely planted in it. Previously it was almost 

 exclusively composed of broad-leaved trees. This year 

 (1919) a Corsican pine was found dead and fallen down, 

 and from its roots I picked the fructification shown in 

 fig. 40. This pine is almost surrounded by larch trees. 



