Page:The Olive Its Culture in Theory and Practice.djvu/149

Rh 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 discharge of resinous matter on the trunk and principal roots, especially of coniferous trees, and by a white creeper which develops beneath the bark of the roots and trunk, and by brown filaments resembling fibrous roots which spread out and run over the ground. The creepers which are first seen are produced from the germination 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 regenerating 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 phosphorescent 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 believed is principally due to this fungus. The tree withers gradually without apparent cause, the climate and chemical or physicial