The other major division of fungi, with about 22,000 described
species is called the Basidiomycota.
These fungi always bear their sexual spores on the outside
of club-shaped mother cells called basidia.
There are usually four spores on each basidium.
A basidium
may be either a single club-shaped cell; a single short, filament-like
cell; or a short, four-celled filament. The basidia
are often arranged in a layer called the hymenium.
The fertile surfaces are produced on, or in, fruitbodies called
basidiomata.
Many of our familiar fungi—mushrooms, puffballs, bracket
and jelly fungi, and also the rusts and smuts—belong to
this division. Everyone knows what a mushroom looks like: it
has a white or coloured cap (pileus)
and a stalk. Turn the cap over and you will see a mass of gills
(lamellae),
pores, teeth, or spines—all formed by the basidia
and hymenium.
The young mushroom is sometimes contained within a universal
veil. When the cap expands this veil is ruptured. One part
is carried up on the expanding cap to remain as patches or warts.
The other half is left at the base and this forms the cup at
the base called the volva.
The base of the stalk is contained within the cup, which is
often hidden underground. In some species the universal veil
may disappear completely. Another
partial veil may cover the gills. When the mushroom matures,
the partial veil breaks away from the stalk, but remnants may
form a ring (annulus)
around the stalk. Mushrooms may lack some or all of these parts.
They exist in many bizarre forms. |
