238 FIRST FORMS OF VEGETATION. 
the water to occur again, or should any change 
be produced in the existing conditions, the 
change, while it would prove fatal to the most 
highly organized of the present race of animals 
and plants, would stimulate into excessive growth 
and profusion animals and plants of the simplest 
construction, which are now kept in check, and 
occupy but the most obscure and subordinate 
positions in the ranks of nature’s agencies. And 
if the advent of wide-spread plagues in the 
middle ages was heralded by the vast develop- 
ment of the conferve and infusoria, we are led 
by a cogent induction to conclude that it is a 
change of the air and water which breeds the 
epidemic, and that these are the first growths of 
that new animal and vegetable kingdom which 
would succeed the existing forms, if mankind were 
to be swept away. 
The subdivision of the conferve to which the 
red snow and the gory-dew belong, contains the 
simplest of all vegetable forms, if, indeed, they 
be plants at all, occurring in shapeless gelatinous 
masses of all hues, covering. irrigated perpen- 
dicular cliffs in dark and shady places, or rocks 
exposed to the spray of waterfalls, and frequently 
hanging down in flakes from their surface. Their 
extreme simplicity is more puzzling to the 
botanist than any amount of complexity would 
