112 



Tree Root Rot. 



[may, 



grows in dense clusters round the roots of living trees, also 

 round dead stumps. In some instances it appears to grow 

 directly from the ground, but careful examination in such 

 cases shows that the mycelium springs from buried wood, roots, 

 &c. It is distinguished by the dingy honey-yellow coloured cap 

 being covered, more especially towards the centre, with small, 

 darker scales ; the stem is coloured like the cap and has a frill 

 or ring near the top ; when young this frill extends from the 

 stem to the edge of the cap and conceals the gills, which are 

 whitish. Myriads of spores are produced, which form a snow- 

 white powder on whatever they fall. These spores are distributed 

 by wind, game, mice, &c., and aid greatly but not solely in 

 spreading the disease. 



Usually the first indication of disease is the drooping and 

 yellowing of the foliage. When the symptom manifests itself, 

 the presence of a thin, firm, white sheet of mycelium, situated 

 between the bark and the wood at the collar, or on the main 

 root-branches, clearly indicates A. uiellea as the cause of the 

 mischief. This felted white mycelium often extends up the 

 trunk between the bark and the wood for several feet, and 

 changes gradually into blackish cord-like strands of mycelium, 

 called rhizomorphs, which continue to grow upwards between the 

 wood and the bark as the latter becomes dry and separates from 

 the wood. These cord-like rhizomorphs become variously 

 branched, and anastomose to form an irregular black network, so 

 frequently met with on removing the bark from a dead trunk, 

 indicating the cause of its death. Black rhizomorphs may also 

 be found surrounding the root-branches. In fact these first in- 

 fect the tree by penetrating the bark of the root and giving 

 origin to the white mycelium. 



Preventive Measures. — When the leaves of a tree droop and 

 turn yellow owing to the presence of the fungus, curative 

 measures are hopeless, as the mycelium has by this time com- 

 pletely girdled the trunk. Nevertheless, it is very important at 

 this period to adopt measures against an extension of the 

 disease. When a tree has been killed the black rhizomorphs 

 surrounding its root extend in all directions about three or four 

 inches below the surface of the ground in search of living roots. 

 When such are encountered, the tips of the rhizomorphs pierce 



