Page:Popular Science Monthly Volume 29.djvu/625

 necks and holds them with firmness; it is a sight once seen never to be forgotten, for their presence shows the decay that has taken place, and conveys an impressive lesson. The bark, like the coat of paint on unseasoned wood, has retained the moisture, the mycelia have grown, and the tree will soon be destroyed and fall to the ground. A study of the decay of trees in the forests teaches many lessons of great importance, and in practice to avoid as much as possible the conditions which there conduce to decay. That the decorticated tree does not quickly decay furnishes a fact of general application in the care and preservation of timber, teaching that wood will be protected by paint only when it is thoroughly seasoned or dry, otherwise the paint will furnish the artificial bark and hasten instead of retarding decay. Readers who are conversant with the decay of freight-cars will understand what must be expected from the use of



so much unseasoned lumber in their construction, and will comprehend the conditions furnished for the growth of fungi by the moisture in-side of the cars retained by the outside paint. These facts must be more generally understood before the car-builder will be supplied with seasoned lumber. There lies before me as I write this a piece of timber from a building erected about eight years ago; to prevent the sills from decay, they were covered on three sides with asphalt, and tarred paper underneath the preparation; the wood was so badly decayed that they were replaced two years since. The wood was cracked longitudinally and transversely, the cracks being filled with the mycelia of the fungi which had destroyed it; upon drying, the wood crumbled to dust—the so-called "dry rot." Planks only two inches thick and eight inches wide were tarred on three sides at the same time, and were rotted under the tar over an inch in depth, while the unprotected side was sound. I did not see these timbers before they were treated, but they reveal their history as plainly as though the words were written upon them; the builder coated un-seasoned wood, and produced the result he wished to avoid.

Fig. 14 is partly in vertical section, to show the pores in which the basidia grow bearing the spores.

On the under side of the various Polyporei here illustrated are the