14 MICROSCOPIC PLANTS. [CHAP. 
putting on a cover-glass, examine it with a high 
power, we shall see a multitude of these little plants 
arranged in strings and heaps. Each plant ranges 
in size from g¢ppth to zoggth part of an inch across, 
or an average of about s,g,th. In other words, it 
would take 3000 of these plants, placed side by side, 
to cover the length of an inch. They increase in 
numbers by budding. A slight protuberance arises 
at one part of the cell-wall, and, rapidly growing, 
assumes the same form and size as the cell from 
which it sprung; though, perhaps, before it gets so 
large, it has itself produced a bud, which has in turn 
produced another. So they multiply at an enormous 
rate, and their growth causes the fermentation of 
fluids containing sugar, which, by the subtraction of 
some of its elements, is changed into alcohol, the 
intoxicating element in beer, wines, and spirits. These 
Torulz are capable of being dried into a powder, and 
in such a condition they form an article of commerce, 
for their vitality is not impaired. They may be kept 
in this state for a considerable period, but on intro- 
ducing a very small quantity into a sugary liquid, 
fermentation will ensue almost immediately as the 
result of their renewed activity and growth. We 
have ourselves kept yeast for nearly three years 
without injury to it. 
But it is time we advanced a step in the considera- 
tion of these minute fungi. We have here a specimen 
of green mould, such as grows on all decaying sub- 
stances—old bread, old boots, jam, dead leaves, &c. 
Carefully selecting a small portion, we place it under 
a low power, and find something like our illustration. 
