136 Potter . — On the Occurrence of Celhilose in the 
devoid of lignin, Marshall Ward finds ‘ during the first month no distinct 
reactions . . . and stains, such as Delafield’s haematoxylin, do not colour 
the walls blue or purple, but merely brown or yellowish ; but in some 
cases a thin lining layer is found to react in wood acted on by the Fungus 
for six weeks to a couple of months, and the altered layer gets more 
and more decided as the action progresses.’ The unequal distribution 
of cellulose make it possible that its presence might have been overlooked 
in the first blocks examined, and no mention of any examination of the 
blocks prior to sterilization is made. I have not had the opportunity 
of studying a quite freshly cut stem of Aesculus of more than about three 
inches in diameter, but, judging from numerous sections of small branches 
and some much larger pieces of Oak, the distribution of cellulose is always 
somewhat irregular, and hence certain of the blocks cut from a good-sized 
stem might be entirely lignified, while in others lignification would be 
by no means complete. In Aesculus this partial lignification occurs more 
especially in the spring wood, and this may explain why it was found 
that c in some transverse sections the spring wood is invaded much more 
rapidly than the autumn wood of the same annual ring ’ when attacked 
by Stereum hirsutum. Marshall Ward’s figure 17 corresponds exactly 
with many sections I have seen of normal wood not attacked by any 
Fungus. 
In his description of tangential longitudinal sections of cultures a 
month old which had been treated with gentian-violet and Congo-red, 
Biffen noted that it was easy to find, especially in the vessels, walls in 
which every pit was marked out by a well-defined, bright pink zone 
surrounding it, indicating that that portion of the wall had been delignified 
and a cellulose basis staining with Congo-red remained. It is significant 
that he observed, moreover, ‘that no hyphae passed through the majority 
of these pits, so that one has to assume the secretion of a delignifying 
enzyme in quantity by the fungus into the wood-elements.’ This appears 
to be an unnecessary assumption which cannot be allowed in face of the 
fact that this appearance is observed very commonly without any Fungus 
being present. That the margins of the bordered pits often remain 
unlignified, especially where the vessel crosses the medullary rays, has 
been demonstrated in the instances above quoted ; and that it is no mere 
optical illusion is shown from the fact of the borders of the pits staining 
distinctly blue upon treatment with iodine followed by sulphuric acid, 
as in Salix (compare Fig. 4). Among herbaceous stems also I have 
observed this ring of cellulose very beautifully shown by chlor-zinc-iodine 
in the large wood-vessels of Cucurbita. 
It has become clear that the presence of cellulose in the wood-fibres 
cannot be attributed entirely to the action of a delignifying enzyme, 
and it is now necessary that the enzyme in each case should be isolated. 
