44 



THE POPULAR SCIENCE MONTHLY. 



to call attention to its destructive influence, its brief technical descrip- 

 tion will not be out of place : " Pileus fleshy, firm, convex, or expanded, 

 nearly white, spotted with dark brown, appressed scales ; lamellae 

 rather broad, not crowded, attached, slightly eraarginate, and decur- 

 rent, white, the edge rough, eroded or torn, stipe firm, solid, equal or 



Fig. l.Lentinus lepideus (Ft.), one half size. 



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 lamellae 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 speci- 

 men 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 my- 

 celiahad followed the longitudinal cells each way, meeting in the cen- 

 ter, between the supports ; the outer portions of the timber remaining 

 dry, did not allow the moisture to escape, and the fungus was destroy- 

 ing the inside, while the outside looked sound. In bridge-plank the 



