DISEASES OF PLANTS. 



layer of mycelium. At this stage the general appearance of 

 the tree clearly shows that something is wrong ; the mycelium 

 spreads up the trunk between the bark and the wood, and also 

 forms dense clusters of toadstools round the base of the trunk, 

 and finally the tree dies. Soon after a tree is attacked, and 

 the fungus is thoroughly established, strands of mycelium 

 radiate in the soil in every direction in search of fresh victims. 

 It thus frequently happens that when the disease is once 

 established in an orchard, several trees are attacked in suc- 

 cession, inoculation taking place by the underground mycelium 

 attacking the roots. The spores of the fungus cannot enter an 

 unbroken surface of the tree, but grow readily on any wounded 

 surface of the trunk near the base, on broken exposed roots, &c. 

 The fungus under consideration attacks not only nearly all 

 kinds of fruit trees, but also forest and ornamental trees, 

 including conifers. Whenever the fungus appears it should be 

 destroyed, not by the usual method of kicking it over, and 

 stamping on it, but by either burying or burning. When clusters 

 of the toadstool grow round the base of a living trunk, it may 

 be taken for granted that the roots are more or less attacked. 

 In such cases the fungus should be cut out, and the wound 

 protected against further chance of infection by a coating of 

 tar. The roots should also be examined, and if found to be 

 more or less covered with white mycelium, should be freely 

 dressed with sulphur and again covered. When a tree is 

 attacked it is advisable to isolate it, by digging a narrow trench 

 nine inches deep round the trunk at a distance of three yards 

 away, so as to check the spread of the underground mycelium, 

 and prevent its reaching the roots of other trees. The soil 

 removed in making the trench should be kept within the trench, 

 and not thrown outside the infected area. 



Other kinds of toadstool also grow in dense clusters round 

 the base of trunks, stumps, decaying posts, &c, but differ from 

 Agaricus melleus in having dark-coloured gills and spores, 

 whereas in A. melleus the spores and gills remain white. 



It may be mentioned as an observed fact that more than one 

 valuable tree has been killed by the careless use of the grass- 

 cutting machine, the base of the trunk or exposed roots having 

 been wounded, such wounds serving as a starting point for the 

 germinating spores of this agaric. 



