124 
Biffen . — On the Biology of 
and then taken through the usual series of alcohols before 
examination for the effects of the Fungus on the wood. 
The only noticeable effect on scrubbing off the external 
mycelium was that the wood was coloured an ochrey-yellow 
tint. Longitudinal and transverse sections of a block infected 
a month before fixing showed that all the tissues were 
thoroughly permeated by hyphae. The large vessels espe- 
cially were crowded with mycelium, all of which showed the 
same swelling of the walls. In some cases the entire lumen 
of a tracheid was blocked by the much-swollen hypha-wall. 
At the same time a slight swelling of the thickening layers 
of the woody elements was visible. On treating transverse 
sections with Schulze’s solution, a few of the most swollen 
thickening layers gave a deep purple colour — suggesting that 
the action of the Fungus was one of delignification. In some 
cases the thickening layers had become detached and invagi- 
nated into the tracheids, owing to excessive swelling, in a 
similar manner to that described by Marshall Ward 1 in the 
case of Stereum hirsutum (Fr.). 
Where the swelling of the thickening layers was slight, 
Schulze’s solution no longer gave either a golden yellow or 
purple colour, but the layers had a peculiar sheen, very like 
that of phloem-tissues, which soon became very characteristic 
of the early stages of delignification. This was followed by 
the gradual appearance of a faint violet and then purple 
colour. The kinking off into the lumen of the tracheid of 
the secondary from the primary thickening layer, or of the 
two together from the middle lamella, was never found to 
occur before their complete delignification. Meanwhile, as 
far as Schulze’s solution showed, there was little change going 
on in the middle lamella ; for it still stained a deep golden 
yellow colour, but in preparations from cultures two months 
old the elements became dissociated from one another, proving 
that it gradually went into solution. 
Longitudinal sections also showed characteristic symptoms. 
The bordered pits of oak-wood seen in surface view, at some 
1 Marshall Ward, ibid. 
