142 College of Forestry 
frequently were encrusted with brown decomposition pro- 
ducts. The decay of the wood within the individual pockets 
was marked by a tendency toward an accumulation of decom- 
position products between the adjoining cavities. In this 
respect it is somewhat analogous to the decay of spruce by 
Trametes pim described by von Schrenk (19007, p. 33). In 
the latter decay, however, a distinct minute dark-brown zone, 
situated midway between two adjoming cavities, entirely 
surrounded the individual cavities. Von Schrenk states that 
a detailed examination of these dark-brown zones showed that 
they were due to masses of dark-brown hyphz which filled 
each wood cell so as to completely occlude it, and that the 
hyphz were encrusted with a brown substance which dis- 
solves in part in dilute potassium hydroxide and entirely in 
warm nitric acid. The brown products encrusting the mats 
of hyphz found in the decayed woods studied to determine 
the course of the decay caused by Polyporus pargamenus 
exhibited the same solubility tests as those enumerated by 
von Schrenk in the rot caused by Trametes pn. As von 
Schrenk (1. c.) observed, the brown encrusting substances 
occur in or on the cell-walls in the immediate vicinity of the 
pockets, and their manner of occurrence leads one to suspect 
that they were deposited in liquid form, for they have dif- 
fused through the various cells in all directions from the 
wall of the cavities. 
As yet the causes which influence this local initiation of 
the physical and chemical changes, which is characteristic of 
several wood-destroying fungi, has not been determined. 
The decay of the light spots progresses rapidly until the 
wood becomes filled with distinct cavities or pockets. The 
hyphe apparently branch out rapidly in all directions from 
each of the original centers of infection, and as they do so — 
the metabolic by-products of decomposition lkewise pass 
outward, passing along the woody elements faster than across 
them. After a period the advancing hyphal masses of two 
adjacent pockets meet in the narrow lamella of unchanged 
wood lying between the two unchanged pockets. By this 
time more or less of the brown substance representing decom- 
