Abstract
Apparently Fomes annosus normally invades healthy, not damaged, roots, the wood being infected almost at once in mall roots, though in larger ones the fungus grows in the bark for some time. Alkaline soils also favour the latter type of development. Infections of living roots are more frequent around infected stumps in alkaline soils than in acid ones. Details are given of infection of pine roots induced experimentally and of the factors affecting invasion. Greater resistance to killing is evinced by older tree and those on the margin of the plantation. Disease is leas severe in East Anglia on acid soils and where there is more organic matter on the soil surface. These relations are apparently associated with the types of soil microflora (of which details are given), the antagonism of Trichoderme viride being especially important.