356 Marshall Ward— On a lily -disease, 
a mycelium exists in the dead cell-walls of the red or brown 
spots, such as that of Fig. 2, and among numerous sections I 
found the one drawn (Fig. 53). In order to make out more 
details it was allowed to swell slowly in very dilute ammonia- 
solution, and the spore then came into view, its germ-hypha 
having entered beneath the cuticle, and grown and branched 
in, and at the expense of the gelatinised cell-walls, which 
were in a collapsed state when the section was cut. 
Such preparations as this and those in Figs. 51 and 52 
leave little doubt that what takes place in infection is as 
follows. The Botrytis - conidium germinates on the damp 
epidermis, and the tip of the germ-hypha excretes sufficient 
of the ferment to soften and dissolve the cell-wall, which 
it then penetrates. Feeding on the substance of the dissolved 
and swollen cellulose, the hyphae grow and branch more and 
more, and excrete larger and larger quantities of ferment. 
The cells thus attacked lose water, and the protoplasm dies 
and turns brown, and finally the whole may collapse, and 
leave simply a shrivelled mass of brown dead cells, in the 
dried-up walls of which the young mycelium is trapped, and 
may persist in a dormant condition. In this way are produced 
the discoloured sunken spots so characteristic of the disease in 
a certain stage. 
If there is sufficient water present to ensure that the swollen 
cell- walls do not dry up, then the hyphae branch and grow 
in the cellulose as shown in Figs. 55 and 56, and soon gain 
sufficient energy to put forth numerous branches downwards 
and in all directions, destroying the subjacent tissues with ex- 
traordinary rapidity (as in Figs. 6 and 7). That the mycelium 
in the small, brown, sunken spots is only in a dormant con- 
dition can be shown by keeping these under a damp bell-jar ; 
it is only because the cell-walls have dried up too rapidly that 
the mycelium lies in a dormant condition, because the ferment 
cannot diffuse and prepare the path of destruction necessary 
for the rapid progress of the hyphae, the growth of which is of 
course also dependent on the presence of water. 
I may now consider the very difficult and involved question 
