The cankers of Exocarpos cupressiformis Labill

Abstract

The morphology and anatomy of cankers formed on Exocarpos cupressiformis Labill. are described. The pathogen is fungal, though it is uncertain whether one or more species of fungus is involved. The cankers consist of a woody framework of lignified, pitted, and distorted fibre tracheids and occasional vessel elements, the pathogen developing in "nests" within this framework. "Witches' brooms" formed on the cankers develop reaction wood. The reaction wood fibres have tannins deposited within their lumina and in the terminal lamellae of "gelatinous" layers. Enhancement of tannin deposition in the wood and bark of cankered trees is one of the main effects of infection. The water-soluble and methanol-soluble extractives in the heartwood of an infected tree were approximately double the amounts in the heartwood of a healthy tree of comparable size.