158 MR. R. H. BIFFEN ON THE 
very local one, quite unlike the action of the hyphe of the 
Botrytis causing the lily disease * for instance, which by 
secreting an enzyme causes the cellulose-walls in its neigh- 
bourhood to swell and dissolve. The solvent action in this case, 
apparently, is exerted directly by the byphe in intimate contact 
with the cell-walls. In badly attacked wood the thickening- 
layers almost entirely disappear, leaving only a little granular 
débris. 
Staining with phloroglucin and hydrochloric acid shows that 
the lignin of the middle lamella, and the corroded thickening- 
layers still persist, even in the remains carried out by the strands 
of hyphe. The powdery débris of the thickening-layers also 
gives the deep pink coloration due to lignin. Chlor-zinc-iodine 
colours the sections a bright golden yellow,except in cases where 
the blocks have been treated with Flemming's solution, when a 
very slight cellulose reaction is sometimes given by the elements 
on the outside of the blocks. These two tests make it evident 
that the lignin of the wood is not destroyed. Had this been the 
case, instead of obtaining a yellow coloration throughout with 
chlor-zine-iodine, a deep purple would have been produced, 
owing to the cellulose reaction being no longer masked by the 
presence of lignin. We can, however, extract the lignin by 
Wisselingh's method t, and thus show it is really cellulose which 
is attacked. For this purpose sections of the infected wood are 
heated to 300° C. with glycerine in sealed tubes for an hour, aud 
then mounted in chlor-zinc-iodine. The lignin dissolves out, 
and the thickening-layers, showing the characteristic pitting, 
give the usual cellulose reaction. This method has the great 
advantage over the acid-extraction method, that it does not cause 
the walls to swell and obliterate their markings ; and further, by 
regulating the time of heating, the lignin may be dissolved out 
from the thickening-layers and yet leave the middle lamella 
intact, so that the sections do not fall to pieces. 
In the paper already referred to Wisselingh has succeeded in 
proving that the walls of fungi do not consist of a special form 
of cellulose known as fungus-cellulose, as it was believed until 
recently, but of chitin similar to that so frequently met with in 
the animal kingdom. On repeating his experiments with sections 
* Marshall Ward, Ann. of Bot. vol. ii. 1898, p. 339. 
t Wisselingh, Pringsh. Jahrb. 1898, p. 619. 
