4 
FETCH : 
which had borne three sporophores had a specific gravity 
of 0-41. 
When cut with a razor, the tissue of the pseudo -sclerotium 
is found to be softer than normal Hevea wood. As a general 
rule, all the elements of the wood are present, but the walls of 
the fibres and of the aells of the medullary rays are reduced in 
thickness. The wall of the fibre in normal Hevea wood 
attains a thickness of 6 ^ ; walls of this thickness may be found 
in the pseudo-sclerotia, but most of them are considerably 
reduced, in some cases to a thickness of about 1 pi, and herè 
and there one finds a pocket ” where the fibres have dis- 
appeared, though the latter occurrence is comparatively 
infrequent. In some cases some of the cells of a medullary 
ray have been destroyed. 
In chlor-zino -iodine the tissue stains yellow-brown. Closer 
examination of longitudinal sections reveals a thin violet 
layer lining most of the fibres. This layer is frequently 
dragged out of the cell in cutting free-hand sections, and is 
then conspicuQus, but it is so thin that it is not discernible in 
cross section. The vessels of the wood and the cells of the 
meduUary rays do not show any blue lining. 
It may be noted that in the sap wood of a healthy Hevea 
the fibres show a thick cellulose lining, which stains violet with 
chlor-zinc -iodine. This sweUs up in the stain, separates from 
the yellow-brown wall, and lies irregularly distorted (in cross 
section) within the lumen of the fibre. The appearance is 
then exactly that figured by Marshall Ward in his paper on 
Stereum hirsvMm (13). Ward states that he used the sap 
wood of Æsculus, and he attributes the inner cellulose layer 
to the action of the fungus, while he gives a complete account 
of the difference in growth of the fungus on the sap wood, on 
which it was luxuriant, and on the heart wood, on which the 
growth was scanty. It would appear possible that the better 
development of the fungus on the sap wood was due to the 
presence of a lining of cellulose in the fibres, suitable for the 
nourishment of the fungus, prior to infection, not to a more 
rapid delignification of the wood by the fungus. 
In the case of a pseudo-sclerotium, the wood of which 
extends from sap wood to heart wood , such as that shown 
