This page has been validated.
THE CULTIVATION OF THE OAK.
161
fungus are able to infect oak planks, beams, etc.; and the mycelium rapidly spreads on and in the wood, destroying the cell-walls, and causing the wood to shrink and crack and warp, and finally to fall to pieces. Thorough ventilation is fatal to the fungus and stops the rot.
![](http://upload.wikimedia.org/wikipedia/commons/thumb/f/fd/The_Oak_%28Marshall_Ward%29_Fig_45.jpg/400px-The_Oak_%28Marshall_Ward%29_Fig_45.jpg)
Fig. 45.—Oak wood destroyed by Polyporus dryadeus, showing the very characteristic markings, like insect tunnels in a deep red brown matrix. (R. Hartig.)
A series of enemies to the oak-tree not yet referred to are various gall-insects, so called because they pierce the young leaves or buds, etc., and lay their eggs in the wound; the irritation set up suffices to induce a flow of food materials to the stimulated spot, and the overfed