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These threads are many times more delicate than the finest hair, 
in fact, they are so delicate that they can scarcely be seen with 
the unaided eye. However, when they occur in large numbers 
these threads give somewhat the appearance of very delicate 
cotton. Such a mass is known as the mycelium (fig. 33) or 
growing phase of the fungus. 
The fungi are propagated by means of special reproductive 
bodies known as spores. The spores may be very simple bodies, 
and among the lower forms are often borne in chains—like strings 
of beads, or they may be more complicated and there is no limit 
to the’ variety of forms which may be assumed by the repro- 
ductive bodies of this group of plants. Among the higher fungi 
special structures are developed for holding the spores. Such 
structures as toadstools, puffballs, and bracket-fungi (fig. 34) 
represent only the spore-bearing phase of fungi whose mycelium 
or growing phase may extend often for many feet into the sub- 
stratum on which they are borne. 
SAPROPHYTES WuicH May BrEcoME PARASITES. 
The blue mould is a fungus with which we are all familiar, 
and one which occurs normally as a saprophyte on decaying 
materials of various kinds, especially on decaying fruit. Often, 
on removing the cover from a can of preserved fruit, a bluish 
scum will be found over its surface. This is the blue mould, 
and the spores of this fungus are produced in such great abun- 
dance that it is impossible to expose suitable materials to the air 
for any length of time without having them infected with this 
great damage to ripe fruit, especially to fruit which is kept in 
storage. This fungus, however, is unable to attack fruit unless it 
is injured in some way and experiment has proved that if stored 
fruit is carefully handled so as to prevent bruising the damage 
from this cause is very much reduced. 
The fish mould is another fungus which normally lives as a 
saprophyte on decaying materials in water. It is doubtful if this 
plant is able to attack healthy fish, but if the bodies of these 
