Page:Popular Science Monthly Volume 29.djvu/456

440 to call attention to its destructive influence, its brief technical description will not be out of place: "Pileus fleshy, firm, convex, or expanded, nearly white, spotted with dark brown, appressed scales; lamellæ rather broad, not crowded, attached, slightly emarginate, and decurrent, white, the edge rough, eroded or torn, stipe firm, solid, equal or



tapering downward, more or less scaly, whitish, sometimes eccentric, straight, or curved. Height, two to four inches; breadth of pileus, three to five inches; stipe, one half to three fourths of an inch thick."

Monstrous forms occur in dark situations with or without a pileus. Only a single stipe and pileus are here shown as emerging from a crevice in the wood; generally two, and sometimes four occur. The small block in Fig. 7 shows the mycelium in the longitudinal resin-ducts (see Fig. 1), which it readily pierces, hastening the destruction of the wood.

On the gills or lamellæ are borne the spores, which are 0·003 of an inch long, and 0·0013 of an inch in diameter, they are curved and one end apiculated; drop out and are carried by the wind to some resting-place; and when the proper conditions occur, germinate, sending out the mycelium, which only fruiting under very favorable conditions from June to September, the fruit is rarely found. I have seen many thousand ties in main tracks destroyed by it, without finding a specimen of the fruit; its mycelium is very abundant, and pierces the coarser cells of the wood with great rapidity, generating sufficient moisture, having an acid reaction, to carry on its destructive work, provided external heat and currents of air are not sufficient to dry the wood.

Examining many pieces of bridge-timber of Pinus palustris (Mill), which were horizontal, I found that where they had rested on others, sufficient moisture had collected to germinate the spores, and the mycelia had followed the longitudinal cells each way, meeting in the center, between the supports; the outer portions of the timber remaining dry, did not allow the moisture to escape, and the fungus was destroying the inside, while the outside looked sound. In bridge-plank the