﻿36 BULLETIN 1128, U. S. DEPARTMENT OF AGRICULTURE. 



darker colored bands of heartwood which are found in some trees, 

 but such bands are confined to a definite group of annual rings. 



EedAvood is subject to a brown friable decay which is not con- 

 fined to the butt of the tree. The fungus causing this is unknown 

 (57). The first indication of the incipient decay is a very faint 

 light brownish discoloration on the light-cherry to deep reddish 

 brown heartwood. This is most readily detected on the tangential 

 face in the summer wood. When the brownish discoloration is 

 plainly apparent, the decay has progressed so far that the affected 

 wood feels softer than the normal to the thumb-nail. The typical 

 decay is dark brown in color, very soft, and easily crumbled. Thin 

 crustlike mycelium felts occur along the sides of the cracks. 



These reddish brown or brown friable decays which are so difficult 

 to detect in their incipient stages, particularly in woods with a pro- 

 nounced reddish or brownish heartwood, reduce the strength of the 

 wood far more serioushy than incipient decays of the red-rot type; 

 in fact, the wood may be weakened before the incipient decay is 

 visible. Consequently, in cutting out such decays from lumber it is 

 advisable to leave a margin of safety of at least 2 feet in a longi- 

 tudinal direction beyond the last visible evidence of the incipient 

 stage. 



Incense cedar is very commonly decayed by the incense-cedar dry- 

 rot fungus (Polyporus amarus Hedge). The typical decay con- 

 sists of vertically elongated pockets, varying in length from half 

 an inch to about a foot, which are filled with a brown friable mass, 

 and the line of demarcation between the sound and decayed wood is 

 very sharp. In some of these pockets small cobweblike or feltlike 

 masses of white mycelium occur. The pockets are separated from 

 each other by what appears to be sound wood, although in some 

 cases streaks of straw-colored or brownish wood may extend verti- 

 cally between two pockets. This is especially noticeable between 

 young pockets. The pockets of incipient decay are at first firm 

 and very faintly yellowish brown. This color deepens slightly, and 

 the wood becomes somewhat soft. The incipient decay extends but 

 a short distance vertically in advance of the typical decay, and a 

 distance of 2 feet beyond the last visible evidence will usually exclude 

 all decajf. The incipient decay is only faintly apparent, occurring 

 as it does in pockets with the color in the very earliest stages differ- 

 ing but slightly, when at all, from the normal wood. The fact that 

 an occasional pocket may be found several feet in advance of the 

 main body of decay makes this decay an exceedingly dangerous one. 

 The wood, even in an incipient pocket is decidely weakened (al- 

 though the intervening wood is apparently not affected), and this 

 makes a weak spot that is hard to detect. Such cases are fortunately 

 not common, and the fact that most incense-cedar stands are so badly 

 decayed will probably preclude this species from any extensive use 

 for airplane construction. Other woods are subject to similar decays. 

 That found occasionally in western red cedar may be caused by the 

 same fungus, while "peckiness" of bald cypress (Taxodium dis- 

 tichum (Linn.) Rich.) results (S3) from the work of a different 

 organism (Forties geotropus Cke.). 



One of the most striking discolorations indicating decay and at 

 the same time one of the most serious incipient decays is that caused • 



