Editing Mushroom (section)

==Morphology==
[[File:Amanita stirps Hemibapha 45069.jpg|thumb|right|''[[Amanita jacksonii]]'' buttons emerging from their universal veils]]
[[File:Lactarius indigo 48568.jpg|thumb|The blue [[Lamella (mycology)|gills]] of ''[[Lactarius indigo]]'', a [[milk-cap]] mushroom]]
[[File:Lycoperdon_perlatum,_Common_Puffball,_UK_,_2.jpg|thumb|''[[Lycoperdon perlatum]]'' (the "common puffball") has a [[gleba]]l hymenium; when young, the interior is white, but it becomes brown containing powdery [[spore]]s as the fungus matures.]]
[[File:Morelasci.jpg|thumb|''[[Morchella elata]]'' asci viewed with [[phase contrast microscopy]]]]

A mushroom develops from a nodule, or pinhead, less than two millimeters in diameter, called a [[primordium]], which is typically found on or near the surface of the [[Substrate (biology)|substrate]]. It is formed within the [[mycelium]], the mass of threadlike [[hypha]]e that make up the fungus. The primordium enlarges into a roundish structure of interwoven hyphae roughly resembling an egg, called a "button". The button has a cottony roll of mycelium, the [[universal veil]], that surrounds the developing fruit body. As the egg expands, the universal veil ruptures and may remain as a cup, or [[Volva (mycology)|volva]], at the base of the [[Stipe (mycology)|stalk]], or as warts or volval patches on the cap. Many mushrooms lack a universal veil, therefore they do not have either a volva or volval patches. Often, a second layer of tissue, the [[partial veil]], covers the bladelike [[Lamella (mycology)|gills]] that bear [[spore]]s. As the cap expands the veil breaks, and remnants of the partial veil may remain as a ring, or [[Annulus (mycology)|annulus]], around the middle of the stalk or as fragments hanging from the margin of the cap. The ring may be skirt-like as in some species of ''[[Amanita]]'', collar-like as in many species of ''[[Lepiota]]'', or merely the faint remnants of a cortina (a partial veil composed of filaments resembling a spiderweb), which is typical of the genus ''[[Cortinarius]]''. Mushrooms lacking partial veils do not form an annulus.<ref>[[#Stuntz|Stuntz]] ''et al''., pp. 12–13.</ref>

The stalk (also called the stipe, or stem) may be central and support the cap in the middle, or it may be off-center or lateral, as in species of ''[[Pleurotus]]'' and ''[[Panus]]''. In other mushrooms, a stalk may be absent, as in the polypores that form shelf-like brackets. [[Puffball]]s lack a stalk, but may have a supporting base. Other mushrooms including [[truffle]]s, [[Jelly fungus|jellies]], [[earthstars]], and [[Nidulariaceae|bird's nests]] usually do not have stalks, and a specialized mycological vocabulary exists to describe their parts.

The way the gills attach to the top of the stalk is an important feature of mushroom morphology. Mushrooms in the genera ''[[Agaricus]]'', ''[[Amanita]]'', ''[[Lepiota]]'' and ''[[Pluteus]]'', among others, have free gills that do not extend to the top of the stalk. Others have [[decurrent]] gills that extend down the stalk, as in the genera ''[[Omphalotus]]'' and ''[[Pleurotus]]''. There are a great number of variations between the extremes of free and decurrent, collectively called attached gills. Finer distinctions are often made to distinguish the types of attached gills: adnate gills, which adjoin squarely to the stalk; notched gills, which are notched where they join the top of the stalk; adnexed gills, which curve upward to meet the stalk, and so on. These distinctions between attached gills are sometimes difficult to interpret, since gill attachment may change as the mushroom matures, or with different environmental conditions.<ref>[[#Stuntz|Stuntz]] ''et al''., pp. 28–29.</ref>

===Microscopic features===
A [[hymenium]] is a layer of microscopic spore-bearing cells that covers the surface of gills. In the nongilled mushrooms, the hymenium lines the inner surfaces of the tubes of [[bolete]]s and polypores, or covers the teeth of spine fungi and the branches of corals. In the Ascomycota, spores develop within microscopic elongated, sac-like cells called [[Ascus|asci]], which typically contain eight spores in each ascus. The [[Discomycetes]], which contain the cup, sponge, brain, and some club-like fungi, develop an exposed layer of asci, as on the inner surfaces of [[cup fungi]] or within the pits of [[morel]]s. The [[Pyrenomycetes]], tiny dark-colored fungi that live on a wide range of substrates including soil, dung, [[leaf litter]], and decaying wood, as well as other fungi, produce minute, flask-shaped structures called [[perithecia]], within which the asci develop.<ref name="Ammirati1985pp25-34">[[#Ammirati|Ammirati]] ''et al''., pp. 25–34.</ref>

In the basidiomycetes, usually four spores develop on the tips of thin projections called [[sterigmata]], which extend from club-shaped cells called a [[basidia]]. The fertile portion of the [[Gasteromycetes]], called a [[gleba]], may become powdery as in the puffballs or slimy as in the [[stinkhorn]]s. Interspersed among the asci are threadlike sterile cells called [[paraphyses]]. Similar structures called [[cystidia]] often occur within the hymenium of the Basidiomycota. Many types of cystidia exist, and assessing their presence, shape, and size is often used to verify the identification of a mushroom.<ref name="Ammirati1985pp25-34" />

The most important microscopic feature for identification of mushrooms is the spores. Their color, shape, size, attachment, ornamentation, and reaction to [[Chemical tests in mushroom identification|chemical tests]] often can be the crux of an identification. A spore often has a protrusion at one end, called an apiculus, which is the point of attachment to the basidium, termed the apical [[germ pore]], from which the hypha emerges when the spore germinates.<ref name="Ammirati1985pp25-34" />