CHAP. XIIL] Fungoid Diseases of Trees 303 



gonidia or spores conveyed easily on the furry coats of mice, 

 &c., or by wind. The colourless mycelium develops through- 

 out the cambium as well as the woody tissue of the roots and 

 the base of the stem. The walls of the cells are penetrated and 

 destroyed by masses of mycelial filaments, so that the whole 

 root-system seems at times to be in a rotten, damp condition. 

 This rottenness spreads from the roots upwards into the stem 

 except in the case of the Scots Pine, whose morbid formation 

 of resin is so great as to check the upward progress of the 

 mycelium. The disease is also noticeable externally by the 

 mycelium protruding from the fissures of the bark in the shape 

 of small yellowish white pustules. The sporophores or spore- 

 producers, of a yellowish-white or pure white colour, are mainly 

 to be found on the roots or at the base of the stem in charac- 

 teristic, large, flat, excrescences which sometimes assume a 

 bracket-like shape; in the old days of flint and steel these 

 fungi made excellent tinder. 



Against direct infection by spores, preventive measures can 

 hardly be taken. Hence protective and remedial measures are 

 alike to be found in the grubbing up an,d removal of all 

 diseased material before it has time to produce the conidia, 

 and in the more general introduction of broad-leaved species 

 of trees into the coniferous woods. Isolation of the patches 

 infected by means of ditches leads to prolific development of 

 sporophores on the roots cut through ; this measure can, there- 

 fore, only be recommended where these latter can be duly 

 removed and burned before there is any chance of their burst- 

 ing and scattering fresh spores abroad. 



B. On Broad- leaved Trees : 



i. Rosellinia quercina, R. Hartig, the Oak-seedling Fungus. 

 This disease attacks the roots of young one- to three-year-old 

 seedling Oaks, especially in nursery-beds and during damp 

 years. It occasions fading and drying up of the plants. The 

 roots appear to be woven round with fine filaments, in the 



