Basidiomycota--The club fungi

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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.

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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