2. Roots of a diseased spruce tree, with numerous small sporophores of polyporus annosus attached. Forestry Bulletin 22, Plate XIII, Figs. 1 and 2.
Of the fungi which attack converted timber, the most important is "dry rot" or "tear fungus" (Merulius lachrymans), Fig. 86. It flourishes on damp wood in still air, especially around stables and ill ventilated cellars. It gets its name lachrymans (weeping) from its habit of dripping moisture.
The fungus destroys the substance of the timber, lessening its weight and causing it to warp and crack; until at length it crumbles up when dry into a fine brown powder, or, readily absorbing any moisture in its neighborhood, becomes a soft, cheese-like mass. * * * Imperfectly seasoned timber is most susceptible to dry rot: the fungus can be spread either by its spawn or by spores, and these latter can be carried even by the clothes or saws of workmen, and are, of course, only too likely to reach sound wood if diseased timber is left about near it; but on the other hand dry timber kept dry is proof against dry rot, and exposure to really dry air is fatal to the fungus. (Boulger, p. 75.)
Fig. 86. Portion of the mycelium of dry rot or tear fungus, Merulius lachrymans. This cakelike mass spreads over the surface of the timber. In a moist environment pellucid drops or "tears" distil from its lower surface: Hence its name. [Ward: Timber; Fig. 21.]
About all that can be done to protect the forest against fungi is to keep it clean, that is, to clear out fallen timber and slash, and in some cases to dig trenches around affected trees to prevent spreading or to cut them out and destroy them. Such methods have heretofore been too expensive to employ in any ordinary American forest, but the time is at hand when such action will prove profitable in many localities.
For the preservation of cut timber from decay, several methods are used. Fungi need heat, air, moisture and food. If any one of these is lacking the fungus cannot grow. Air and heat are hard to exclude from wood, but moisture and food can be kept from fungi. The removal of moisture is called seasoning, and the poisoning of the food of fungi is a process of impregnating wood with certain chemicals. Both these processes are described in Handwork in Wood, Chapter III.
ANIMAL ENEMIES.
The larger animals working damage to our forests are chiefly rodents and grazing animals. Beavers gnaw the bark, while mice and squirrels rob the forest of seed and consequently of new trees. The acorns of white oak are particularly liable to be devoured because of their sweetness, while those of red and black oak, which afford timber of comparatively little value, are allowed to sprout, and thus come to possess the land. Hogs annually consume enormous quantities of "mast," i.e., acorns or other nuts, by pasturing in oak and other forests. They, together with goats and sheep, Figs. 87 and 88, deer and cattle, work harm by trampling and browsing. Browsing destroys the tender shoots, especially of deciduous trees, but trampling entirely kills out the seedlings. The cutting up of the soil by the sharp cleft hoofs injures the forest floor, by pulverizing it and allowing it to be readily washed away by storms until deforestation may result, as was the case in France after the Revolution. It has cost the French people from thirty to forty million dollars to repair the damage begun by the sheep. In this country, this matter has become a very serious one on the Pacific Coast, where there are enormous flocks of sheep, and therefore the government is trying to regulate the grazing on public lands there, especially on steep slopes, where erosion takes place rapidly.[1]
