﻿DECAYS AND DISCOLOEATIONS IN" AIRPLANE WOODS. 39 



A somewhat similar rot in oaks (34) is the honeycomb heart-rot 

 (Stereum subpileatum B. and C). As in the whitish piped rot, the 

 first indication of this decay in white oak is a slight water-soaked 

 appearance of the fresh heartwood, and when dry this " soak " be- 

 comes a tawny color. Next, light-colored isolated areas appear in 

 the tawny discolored wood, and pronounced delignification occurs. 

 This is indicated by the appearance of very small irregular whitish 

 patches in the light-colored areas. These patches develop into small 

 pits with their long axes parallel to the grain of the wood, and they 

 increase in number until the affected wood is completely occupied. 

 The pits are from one thirty-second to one-fourth of an inch wide 

 by one-fourth to five-eighths of an inch long, and lined with cellulose 

 fibers. At this stage the appearance of the decay is similar to the 

 red-rot in softwoods previously described. Later the cellulose lining 

 may disappear. The wood is probably not weakened by this decay 

 until the light-colored areas appear in the tawny discoloration. 



An incipient decay is sometimes encountered in African mahog- 

 any, the cause of which is unknown to the writer. This decay ap- 

 pears as light-yellow, brown, or merely lighter brown closely crowded 

 spots or flecks on the reddish-brown heartwood. These flecks vary 

 from one-sixteenth to one-quarter of an inch long and are several 

 times longer than broad, the long axis corresponding with the direc- 

 tion of the grain in the wood. Such wood is weakened. 



TYPES OF DECAY IN LOGS AND LUHBEK. 



In addition to the wood-destroying fungi which normally attack 

 living trees, and which may continue to decay the wood after the 

 tree is cut, there are fungi which grow only or principally on wood 

 in the form of logs or lumber. Owing to their clestructiveness, some 

 of these deserve more than passing mention. Although it is true 

 that damage caused by such fungi is due to improper handling of 

 the timber during the course of manufacture and utilization, unfor- 

 tunately such improper handling does occur and must be reckoned 

 with. 



/Softwood logs and lumber. — One of the most important of these 

 fungi is that which causes dry-rot in stored logs or lumber and in 

 timber in structures (22). The term "dry-rot" is loosely applied 

 to cover almost any type of decay, but it is correctly applicable 

 only to the work of the dry-rot fungus (Merulius lacrymans (Wulf.) 

 Fr.). This decay is more common on coniferous woods than on 

 hardwoods. The incipient decay appears as a yellow-brown dis- 

 coloration not easy to detect. Wood with typical decay is yellow to 

 brown in color, much shrunken and cracked, and is so badly disin- 

 tegrated that it can be easily crushed to a powder. Both sapwood 

 and heartwood are attacked. 



Another common decay on logs and sawed lumber, particularly 

 on railroad ties, is the brown- rot (62) caused by the brown Lenzites 

 (Lenzites sepiaria (Wulf.) Fr.), which is practically confined to 

 coniferous wood. The typical decay is brown, friable, and easily 

 reducible to a powder. In the early stages of decay infected wood 

 is darker in color than the normal. Sometimes the early spring 

 wood of the annual rings may be completely decayed, while the 



