FUNGI. 325 
however, better understood than they formerly 
were; and although the controversy is still 
going on with. unabated interest between the ad- 
vocates and the opponents of the doctrine of spon- 
taneous generation, the balance of proof appears 
to me to be decidedly on the side of the latter. 
The beautiful researches. of M. Pasteur, models 
alike of scientific experimentation and logical 
reasoning, have, as far as I can judge, established 
the fact, that a seed is as necessary for the pro- 
duction of the minutest speck of mouldiness which 
the microscope can reveal to our view, as the acorn 
is for the germination of the giant oak of the 
forest, or the date for the growth of the magnifi- 
cent palm of the desert. It is true that fungi are 
most frequently found on the products of animal 
or vegetable decomposition; but they occur in 
such situations, not because these decaying sub- 
stances originate them, but because they afford 
them the necessary conditions of their growth, 
their germs having been previously deposited there 
by pre-existing species. If we sow a quantity of 
the spores of the common bread-mould on a stale 
crust, we shall have a quicker growth and a more 
abundant crop of fungi than if the crust be left to 
a natural or chance supply of seeds; just as the 
farmer has a surer and more plentiful harvest 
when he deposits a sufficient quantity of seeds in 
