THE OLIVE 



121 



AGARICUS MELLEUS. 



{Root rot.) 



This fungus has a flat, thin, scaly top with a fluted expanded 

 margin and spongy stalk. On first appearing, it is whitish, but 

 afterwards becomes mottled with red. Spore a floury white. The 

 hairs which are found on the head are black. It is found at the 

 base of coniferous and fruit trees as well as the olive tree. 



Its vegetable system is wrapped about the subterranean part of 

 the tree, and its presence can be recognized by an abundant dis- 

 charge of resinous matter on the trunk and principal roots, especi- 

 ally of coniferous trees, and by a white creeper which develops be- 

 neath the bark of the roots and trunk, and by brown filaments re- 

 sembling fibrous roots which spread out and run over the ground. 



The creepers which are first seen are produced from the germin- 

 ation of the spore. Developing from this, the parasite shews itself 

 on the roots, in the form of a filament or creeper, the outer covering 

 being smooth and dark, while the pith or marrow is white. These 

 creepers take root in the wood, penetrating the pith and spreading 

 out until in the form of a membrane, they fix themselves in the re- 

 generating zone. By some writers this root rot has been given the 

 name of Rhizomorpha subcorticallus. In a fresh state it has an 

 agreeable odor and seen at a distance in the dark it has a phosphor- 

 escent appearance. 



The regenerating zone attacked by the Rhizomorpha ceases to be 

 prolific as the formation of new wood has been interrupted. 



The cellular and fibrous elements invaded by these tendrils turn 

 brown. 



After this plant has devastated the lower part of the trunk of 

 the tree, it spreads upward to the surface of the ground, showing 

 itself in the autumn through crevices in the bark. The decay of 

 the Mulberry, Chestnut, Fig, and sometimes citrus trees, it is be- 

 lieved is principally due to this fungus. The tree withers gradually 

 without apparent cause, the climate and chemical or physicial con- 



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