Division Basidiomycota (also called Phylum Basidiomycota) accounts for about 37% of all described fungal species. This division contains the fungi that people are most familiar with. The classic “Mario mushroom” (based on Amanita muscaria), the grocery store button mushroom and other varieties of Agaricus bisporus, shiitakes, oyster mushrooms, and even the major “magic mushrooms” are all basidiomycetes. However, the Basidiomycota also include rusts and smuts, which are economically important plant pathogens, some yeasts, and a few lichenized fungi. Like the Ascomycota, the Basidiomycota fill a variety of different ecological roles. Many form mycorrhizas with plants, others parasitize plants, a lot decompose organic material, and some live in a variety of symbioses with insects. The Basidiomycota are commonly referred to as “basidiomycetes,” “basidios,” or “club fungi.”
describing the physical characteristics of fungi
The gilled mushrooms, informally referred to as ‘agarics,’ are the type of mushroom with which we are most familiar. The most common edible mushrooms (white/button/portabella mushrooms, oyster mushrooms, and shiitake mushrooms), Amanita muscaria – the most recognizable mushroom in the world and the inspiration for almost all mushroom art – and the ‘magic mushrooms’ are all gilled mushrooms. All these mushrooms share one feature: vertical plates of spore-producing tissue stacked under a sterile cap.
Cortinarius contains umbrella-like agaric mushrooms that are mycorrhizal, have a brown spore print, and produce a cobweb-like partial veil. It is the largest mushroom genus on Earth, with over two thousand species crammed into it. While the genus itself is fairly easy to recognize, identifying anything down to species is next to impossible. Most of the species listed in field guides are actually species groups and the field guide descriptions apply to a handful of closely related species.
The stropharioid mushrooms include agarics from the genera Stropharia, Hypholoma, Psilocybe,* and Pholiota. Mushrooms in this group produce a brown to dark brown spore print, have attached gills, and form a partial veil. There are actually quite a few mushrooms that can fit this description, so you might have to check some microscopic features to be sure your mushroom belongs to this group. Stropharioid mushrooms should have a cap surface composed of thread-like cells and have smooth spores with distinctive germ pores.
The family Pluteaceae contains umbrella-like agarics with pink spores and free gills. Within the group, most mushrooms are divided among the genera Pluteus and Volvariella. Pluteus mushrooms grow only on wood and never produce a volva, while Volvariella species grow on a variety of substrates and always form a volva.
The Entolomataceae are agarics with pink spore prints, attached gills, and spores with sharp corners or bumps. This family is very diverse and morphology varies widely from one species to the next. The mushrooms range in size from small to large, though most are on the small side. A majority of the Entolomataceae are just boring mushrooms, so they are not collected very often. This is probably just as well, since identifying these mushrooms down to species is a herculean task.
The waxy caps (alternately called “wax caps” or “waxcaps”) are agaric mushrooms primarily distinguished by their waxy texture, as the name suggests. Actually, the gills are the only part of the mushroom that feels waxy. To fully appreciate the unusual texture, break off a small piece of the gills and roll it between your fingers. It should have a texture reminiscent of soft candle wax.
Pleurotoid mushrooms are agarics that have a single common feature: they lack a well-developed stipe. Originally, I was not going to include pleurotoid mushrooms as a distinct agaric morphology. Their other physical characteristics vary widely and they belong to multiple unrelated taxonomic groups. To anyone classifying mushrooms, grouping them based on pleurotoid growth is decidedly unhelpful. However, it is a useful group from a field guide standpoint because it quickly reduces the number of possible matches. Eventually, I decided to discuss the pleurotoid mushrooms because they are often mentioned in field guides and because “pleurotoid” is a commonly-used mushroom descriptor.
Crepidotus species are small, brown-spored agarics that grow on wood and either lack a stipe or have a diminutive stipe. These features are usually enough to separate Crepidotus species from mushrooms with a similar habitat and morphology; most other morphologically similar mushrooms produce pale spores. Although commonly encountered, Crepidotus is not useful for anything and the mushrooms go ignored by most seasoned foragers.
The family Gomphidiaceae is small but easy to identify. Mushrooms in this group produce gray to black spores, have decurrent gills, and are shaped like tent pegs. All the fungi in the Gomphidiaceae are mycorrhizal and have some degree of a slimy cap. This is not surprising since their closest relatives are the slimy-capped boletes in the genus Suillus.