198 TRANSACTIONS OF THE ROYAL CANADIAN INSTITUTE [VOL. XII 
disintegrating action of its own mycelium, and such cavities are sub- 
sequently more or less filled with masses of mycelium. A striking ex- 
ample of this is illustrated in Fig. 4, a mass that came from the centre 
of a five-foot pine log left in an Ontario forest during lumbering opera- 
tions. The entire log was badly decayed by Fomes officinalis, and on 
the middle of one end there grew a single fruiting body. Two or three 
years after the removal of this, another took its place; and on removing 
this one, I noticed that it was attached to a mycelial core, perhaps two 
inches in diameter. On opening up the log, it was found that the centre 
was occupied by a cavity, in some places 6 inches in diameter, and that 
this was lined with a tubular, cylindrical mycelial core—not unlike a 
length of white fire hose with the lower wall much thicker than the 
upper. This core was followed for six feet, as far as operations were 
carried, and was seen to continue farther. The interior of the tube was 
a fairy land of purest white, studded with glistening drops of clearest 
dew-like exudations, and the floor like the rugged bed of a mountain 
stream paved with closely crowded, exquisitely white mycelial boulders 
of many sizes and forms. 
The resemblance of the mycelial sheets of Fomes officinalis to those 
of Polyporus sulphureus has already been pointed out, a feature that 
may indicate some relationship between these two forms, all the more 
striking as P. sulphureus sometimes attacks conifers. But there are 
differences, confirming the observations made on my cultures, that 
clearly establish the independence of the two species. The mycelial 
sheets of Fomes officinalis are generally more regular and abundant, 
they are more subject to the disintegrating effects of bacteria and 
weathering, and they are differently constituted. This last feature is 
determinative. The mycelium of F. officinalis consists of white, rather 
closely-interwoven, thick-walled threads of great fineness and uniformity, 
mostly 1.54 in thickness, but sometimes up to 2u. They are smooth, 
and rarely septated; there are few clamp-connections, and branches 
are given off at infrequent intervals and characteristically at right 
angles (Fig. 30). The mycelium of both species is sometimes covered, 
to a limited extent, with resinous secretions in the form of irregular 
granules, especially in the sheets. The mycelium of P. sulphureus, on 
the other hand, is marked by a lack of uniformity, for while a large pro- 
portion of the threads may be fine, down to I.5u in diameter, smooth, 
and thick-walled, these slender threads are branches of coarser hyphae, 
the main trunks measuring up to 6.5u. The proportion of fine branches 
and coarse trunk threads is very variable. In old, thick sheets the 
hyphae may become encrusted. Branching, likewise, may be frequent, 
and is ordinarily at an acute angle. 
