Brown : Timber Rot 
3 
infected wood. These are usually discoid in shape and about the 
size of the head of a pin. More rarely, narrower brown areas 
occur which are elongated lengthwise of the log. In such cases 
the hyphal wefts arise from seasoning checks in the wood; the 
first case is by far the most frequent. Usually several, or as 
many as a dozen, of these small brown disks arise in the area of 
a square inch. 
The manner of growth of the brown disks, oncd formed, de- 
pends on their position with reference to the substratum. If 
they occur laterally on a log, dimidiate fruit bodies are formed; 
if on the under side, wholly resupinate forms arise. In either 
case, growth goes on all along the margin of the disk for a time. 
Subsequently, in the dimidiate forms, the upper margin continues 
its growth, arches out away from the substratum, and forms the 
pileus. The lower margin continues to expand for a short time 
downward along the substratum and may unite with other fruit 
bodies, but eventually, and much sooner than the arching upper 
margin, ceases to grow. The final result is a cluster of shelving 
fruit bodies, partially coalesced behind next to the substratum, but 
with separate free outer margins. 
The development of the wholly resupinate forms is easier to 
follow. Growth is much more regular along the margin and may 
continue so evenly that circular fruit bodies are formed. Usu- 
ally, however, owing to the irregularities of the substratum, 
growth is restricted here and there so that the contour of the 
fruit bodies becomes irregular and sinuous. This appearance is 
still further enhanced because the fruit bodies often coalesce 
(Fig. 21 ). Two advancing margins meet and the hyphae inter- 
mingle. The line of union remains distinct for a time as a pubes- 
cent ridge through the hymenium, but eventually the latter covers 
this and the line of delimitation between the two fruit bodies is 
obliterated. In this way, extended hymenial layers are formed in 
the resupinate type. Evidence of their synthetic origin may be 
observed, however, by carefully removing them from the sub- 
stratum and examining the surface next to the wood. In such 
a case, one finds as many points of attachment as there are units 
entering into the structure of the compound sporophore. 
Age of Fruit Bodies.— The fruit bodies of Hymenochaete rub- 
