PSEUD O -SCLEROTIA OF LENTINUS SIMILIS, &C. 
9 
As has already been noted, the red limiting layer of the 
pseudo-sclerotium resembles the black layers found so fre- 
quently in wood attacked by Pyrenomycetæ. The opinion 
seems to be current that in the latter instances the black 
layer indicates the limit to which the mycelium of the fungus 
has advanced. That view would appear to be untenable in 
the present case ; the enormous development of thick-walled 
mycelium and the comparatively slight destruction of the 
wood preclude the suggestion that the remainder of the tissues 
have been destroyed by some other agency. 
Some features in the supposed course of development of 
P achy ma cocos would appear to bring it into relationship 
with the pseudo-sclerotium of Lentinus similis. Pachyma 
cocos is a subterranean sclerotium which is frequently found 
united to the roots of trees. The relationship between the 
root and the fungus has been described by Fischer (3), from 
whose account the following details are taken. In an 
example in the Herbarium of the British Museum, the strongly 
developed Pachyma sclerotium was seated on a fairly thick 
root and surrounded by a dark rind. In a cross section the 
wood of the root appeared intact. There was no Pachyma 
mass within the wood, but it was situated between the wood 
and the cortex, the latter forming the outer dark rind. In a 
specimen at Kew the white Pachyma mass was not limited 
to the space between the wood and the cortex, but had attained 
a fair development within the wood ; the greater part of the 
wood had been replaced by hyphæ, but in cross section it was 
seen that wedges of wood remained, projecting inwards from 
the periphery. In a third specimen a cross section showed 
that nearly the whole mass consisted of fungus hyphæ, and 
only traces of wood remained ; the latter consisted of scattered 
groups of cells towards the periphery, and a great number of 
isolated discoloured fibres in the central parts. 
Microscopic examination showed that the Pachyma consti- 
tuents were not confined to the white masses which to the 
naked eye were obviously of fungus origin, but that these 
were present also within the cells of the apparently sound 
wood. They occurred in all the elements of the wood ; in 
the majority of the sections hardly a single cell could be 
6 ( 6)15 ( 2 ) 
