356 FIRST FORMS OF VEGETATION. 
on decaying succulent fruits, on bread when kept 
too long in a warm and damp situation, on old 
shoes laid aside, on clothes and other articles of 
common wear. There are several genera and 
numerous species included under the one popular 
name. Of these the most familiar is the d/ue 
mould, belonging to the genus Aspergillus (Fig. 
36), so called from the resemblance of its 
fructification to the aspergillus or brush used 
for sprinkling holy water in Roman Catholic 
Fic. 36.—(a) ASPERGILLUS GLAUCUS. (6) ASPERGILLUS CANDIDUS. 
countries. This species is of very frequent 
occurrence on decaying substances of all kinds, 
and gives a white and downy, or a blue-grey 
and powdery aspect to the objects on which it 
grows. Another exceedingly common species 
is the green mould, belonging to the genus Peni- 
cillium (Fig. 37). It presents a close resemblance 
to the former species, but differs in this respect, 
that its spore-bearing stem divides into numerous 
