370 Biffen . — A Fat- Destroying Fungus. 
The piercing of the walls is evidently brought about by the 
secretion of a cellulose-dissolving enzyme, for they swell 
strongly, and the hyphae push their way directly through 
the gelatinized walls without showing any signs of constric- 
tion. The hyphae, on reaching the walls to be pierced, either 
swell directly into a bulbous ending, or give out two or three 
short branches, which then dilate and apply themselves to the 
wall. These endings each contain a large nucleus which 
stains deeply with haematoxylin, numerous small vacuoles, 
and oil-drops (Fig. n). It is probable that they secrete the 
cellulose-enzyme, which presumably gelatinizes the cell-walls, 
just as the haptera of the Lily-disease Botrytis do 1 . The 
walls are pierced and dissolved to such an extent that in 
cultures six weeks old it is difficult to find a trace of the 
endosperm cell-walls, the whole mass being reduced to a slimy 
pulp, through which the mycelium runs in all directions. The 
hard brown testa undergoes little change, and that mostly 
mechanical, owing to the mycelium breaking through it and 
carrying out fragments into the stroma. No action on its 
thickened cell-walls could be detected. Meanwhile some 
very obvious changes have been brought about in the oil- 
contents of the endosperm ; for, instead of large masses of fat 
being present in the attacked cells, the quantity has become 
exceedingly small, being in many cases only represented by 
a small quantity of a fine emulsion. 
This is especially well seen in longitudinal sections of cul- 
tures two weeks old stained for six hours in an alcoholic 
extract of alkanet-root. They appear to the naked eye to 
be composed of alternating bands of deep and pale red tissue 
(Fig. 9). Under the microscope the unattacked cells are 
found to be full of the deeply stained oil, while in the attacked 
cells the oil is chiefly to be found in the mycelium. So 
abundant is it there that it is an easy matter to trace the 
course of the hyphae through the cell-walls by means of the 
dark red drops. 
In cultures in which the stroma has been formed, the dis- 
1 Marshall Ward, Ann. of Bot., vol. ii, p. 339. 
