126 Biffen . — On the Biology of 
readily traced in preparations from cultures six or eight 
weeks old. In these all stages of delignification were visible 
as a rule. 
In the portions least attacked the thickening layers of the 
various elements were still stained an intense blue, except in 
the immediate region of pits, where the pink staining again 
indicated delignification, while in the portions most attacked 
they were pink throughout. The effect of the action of the 
Fungus on the middle lamella was also beautifully shown. At 
first the lamella stood out sharply as an intensely blue line, 
which gradually became thinner and thinner until it entirely 
disappeared, except at the corners where several cells met. 
Where the sections had passed through a pit the lamella was 
wanting on either side for some distance, and if the action 
had only just started, a lens-shaped patch of delignified tissue 
was clearly marked off round it (Fig. 4). In still more dis- 
eased portions the gradual disappearance of the angular 
portions of the middle lamella was traceable. They first 
became hollow owing to the solution of the so-called ‘ inter- 
cellular protoplasm’ of Russow 1 and then dissolved entirely 
(Fig. 5). In this* stage the various elements were separated 
from one another and the wood readily crumbled away on 
sectioning. As far as my cultures go, this entire breaking 
up of the wood was of very local occurrence. It was never so 
complete as in the case of Stereum frustulosum , for example. 
All the woody elements were attacked in precisely the 
same way, and at about the same period, with the exception 
of the tracheids of the medullary rays. These resisted the 
attack for some time and stood out as dark blue bands, in 
transverse sections, when almost the whole of the lignin had 
disappeared from the other elements. Ultimately they too 
were attacked, however, the action starting most frequently 
at the point where they abutted on a vessel. 
The early stages of this localized delignification of the walls 
resemble the early stages in the destruction of the thick 
cellulose walls of the endosperm of germinating seeds of 
1 Gardiner, Proc. Camb. Phil. Soc., vol. v, pt. ii. 
