FUNGI. 363 
matter gradually assumes the condition of active 
vegetative growth. The germs of the mould, 
which had been incorporated in the material, 
begin to live and expand, each bearing a distinct 
plant, giving rise either by gemmation or nuclea- 
tion to new plants indefinitely, until the entire fer- 
menting principle is exhausted. The form which 
the Zorula cervisig or yeast-plant assumes is that 
of a number of small spherical vesicles, which when 
mixed with the wort of beer speedily produce one 
or two gemme or buds. These buds grow to the 
size of the parent cells, and produce new buds ; so 
that in several hours a string of cells is formed 
like a necklace of beads. By the time that five or 
six vesicles are strung together, the fermentation 
is sufficiently advanced, and the manufacturer 
checks it. The vegetation is then suspended, and 
the groups of vesicles separate into individuals, the 
mass of which thus constitutes the yeast. The 
cells of the yeast-plant are globular at first, but 
they gradually change, while the fermenting prin- 
ciple is being used up, into the oval form ; when 
the sugar is still more exhausted, they become 
linear and filamentous, advancing to the primary 
stage of mycelium; until finally, when the whole 
fermenting matter is absorbed and evaporated, they 
develop into the normal crust and organs of fructi- 
fication of the common Penicillium or blue mould. 
