364 FIRST FORMS OF VEGETATION. 
Yeast is very tenacious of its vitality, its power 
of growth not being destroyed either by a heat 
almost equal to that of boiling water, or by a cold 
_ of 76° below zero, or by being completely dried up. 
For what purpose, it may be asked, were plants 
so excessively numerous, and so universally dis- 
tributed, created ; for to many individuals they 
are such objects of prejudice and disgust, that 
their real importance as useful productions is little 
appreciated? We do not know indeed a// the wise 
purposes which He who created nothing in vain 
intended them to serve in the economy of nature ; 
but we are acquainted with some of them, and 
these are so obvious and important, and reveal 
such striking examples of adaptation of means to 
ends, that we cannot but lament that such ignor- 
ance and prejudice regarding them should exist in 
this country. There is no elementary and self- 
subsistent organic matter in nature, as Buffon 
erroneously taught ; and the health and wellbeing 
of man himself may more or less immediately de- 
pend upon the offices which these despised pro- 
ductions perform. We have seen the effect of 
fungi in the two great processes of fermentation 
and putrefaction, which are of such vast importance 
in the economy of nature and art, and whose 
true cause and nature are now only being under- 
stood. Appearing as they do in those months of 
