Basidiomycota--The club fungi
While this
division is not as large as Ascomycota, it is probably better known to you. It
includes the common mushrooms, toadstools, bracket fungi, puffballs, and the
rusts and smuts. The latter two groups are parasitic on many of our important
crop plants. We are rarely aware of the vegetative mycelium; it grows in the
organic matter of soils, in rotting logs, etc. The mushroom, etc., with which
we are familiar, is the reproductive structure or basidiocarp formed by an intricate mass of interwoven dikaryotic hyphae. Basidiocarps vary
greatly in appearance in different genera, but all bear basidia which are usually arranged in a layer of hymenium. The basidium, like the ascus,
is the site of karyogamy and meiosis.
The basidium is a club-like cell at the end of which are four short
stalks (sterigmata), each of which
extrudes one of the four basidiospores.-
Observe the gross aspects of a
common edible mushroom (Agaricus). In
the arboretum you learned that the basidiocarp of some mushrooms include a volva, a stipe, an annulus, and a
pileus (cap). Look at the
under-surface of the cap of the mushroom; note the gills with lamellae
radiating from the center to the periphery. The surface of the gills is a hymenium made up of closely packed basidia bearing basidiospores.
Sketch:
Agaricus (10 points)
pileus
lamellae
annulus
stipe
|
Coprinus (8 points) use highest magnification!
basidiospores
sterigmata
basidium
dikaryotic cells
|
Examine a
prepared slide of Coprinus, a
mushroom, which shows sections of gills lined by basidia with basidiospores.
Most of the latter may have become detached from the basidia during the
preparation of the slide. Note the intertwined hyphae which make up the tissue
of the gills.
Are
these hyphae septate or coenocytic?
Closely examine basidia along the surface of the
lamellae (gills) to find one showing all four basidiospores on the tips of four
sterigmata (tips). If you find a good one, call the instructor over so the rest
of the class can see this…and include that basidium in your sketches above.
Some
mushrooms you might pick up on a hike do not have gills under their caps. They
may have a sponge-like hymenium composed of many small pores. These are the
so-called polypore mushrooms. Examine a prepared slide of some of this hymenium
in Polyporus. Locate basidia and
basidiospores. Sketch (6 points):
Polyporus: basidia
basidiospores
dikaryotic cells
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