354 DR. w. &, M‘NAB. 
of a much-branched, hyphal system, in the middle of a 
tissue which is not directly of sexual origin, but stands 
in close relation to the sexual act, and is a consequence of 
it. This tissue is descended from the hyphe of the 
sexual generation, and forms a protecting covering to the 
young germ, and, as we shall presently see, serves for its 
nourishment. ‘The greatly thickened cells and the protec- 
tion externally by cork-cells indicate a condition of perma- 
nence and rest; in this condition the structure may be 
termed a sclerotium. In its mode of origin and nature the 
sclerotium of Penicillium agrees in its general characters with 
the endosperm-bearing seed of the higher plants. The 
seed contains the germ (embryo) of the second asexual 
generation, and a sterile tissue belonging to the sexual gene- 
ration. This sterile tissue is the endosperm on which the 
embryo lives at a later period after the termination of a 
period of rest, and when the conditions for germination are 
present. 
In order to study the further changes, the sclerotia must 
be made to germinate. They were first washed thoroughly, 
to free them from all impurities, then placed on several 
layers of filter-paper, and covered with a bell-glass. The 
paper was renewed in from fourteen days to three weeks, and 
the sclerotia carefully washed. At first the sclerotia re- 
mained unchanged, except that the outer wall became dark 
brown. At intervals of three or four days the sclerotia were 
examined, but it was not until after five or six weeks that any 
change could be observed. ‘The contents of the cells next 
the carpogonium-hyphe became turbid; the small cells 
became withered, and their walls lost their shining and 
highly refractive appearance. ‘This was only observed at 
certain parts near the centre of the sclerotia. ‘The carpo- 
gonium-hyphe develop septa, and become divided into 
short cylindrical cells (Plate X VII, fig. 5 c). ‘These individual 
cells, which do not separate, now begin to branch in a 
peculiar way. <A thick branch is formed, the apex and 
short lateral twigs of which coil up in a snail-like manner. 
At the same time a thin branch is formed from the same 
cell, which has the appearance of an ordinary hypha, and 
grows greatly in length, twists upon itself like a tendril, and 
forms similar lateral branches (Plate, XVII fig. 6). Many 
cells of the carpogonium-hyphze produce no branches. 
Sometimes two or three cells lying together produce branches, 
at other times only one; and Brefeld was unable to 
determine whether the other cells subsequently produced 
branches or not. 
