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more rigidly supported surfaces can release the
spores by active processes. For example, the asci of
many Ascomycota function as small guns, shooting
ascospores to 1 or 2 cm distance, to break free of the
boundary layer. Spores can also “pop” from a supporting
structure when an enclosing wall layer suddenly rup-
tures, like two balloons that pop apart if compressed
and suddenly released (e.g. Conidiobolus).
Some other fungi are dispersed by rain-splash. In
these cases the spores often are linear or curved (e.g.
Fusarium, Fig. 10.24) and are produced in mucilage
on a pad of tissue (an acervulus) or in a splash cup so
that raindrops are caused to fragment on impact and
rebound as many tiny droplets which can carry the
spores into the air. Splash cups are also found in a group
of Basidiomycota that grow on decomposing wood
chips, on the surface of organic soils or on dung. A good
example is the genus Cyathus(see Fig. 2.21).
Raindrops or hail can also release dry spores that
are lying on a surface, by “puff” and “tap” mechanisms.

When a raindrop falls on a rigidly supported surface,

the drop splodges sideways, and the resulting puff

of air disturbs the boundary layer, causing the dry

spores to become airborne. Hailstones act differently –

they are most effective in redistributing spores from

lightly supported surfaces such as leaves. In puffballs

(Basidiomycota) such as Lycoperdon (see Fig. 2.23) the

mature basidiospores are enclosed in a papery fruitbody

with an apical pore, so that raindrops “puff” the

spores into the air, like bellows.

Toadstools display a different strategy from all those

above, made necessary by the deep layer of still air

that often exists on a woodland floor. When the stalk

(stipe) of a toadstool elongates, the cap (pileus) projects

into turbulent air. The basidiospores develop on short

stalks (sterigmata) and the spores are popped from the

stergimata when the continuous outer wall surround-

ing the sterigma and the spore breaks down, so that

the spores can drop from the gills or pores and be car-

ried away by wind. Much of the variation in shape and

FUNGAL SPORES, SPORE DORMANCY, AND SPORE DISPERSAL 205

Fig. 10.24Curved spores (macroconidia) with several compartments, typical of many species of Fusariumand other
splash-dispersed fungi.

(a)

(d) (e) (f) (g)

(b) (c)