Polypore

Bracket fungi, or shelf fungi, are among the many groups of fungi that compose the division Basidiomycota. Characteristically, they produce shelf- or bracket-shaped or occasionally circular fruiting bodies called conks that lie in a close planar grouping of separate or interconnected horizontal rows. Brackets can range from only a single row of a few caps, to dozens of rows of caps that can weigh several hundred pounds. They are mainly found on trees (living and dead) and coarse woody debris, and may resemble mushrooms. Some form annual fruiting bodies while others are perennial and grow larger year after year. Bracket fungi are typically tough and sturdy and produce their spores, called basidiospores, within the pores that typically make up the undersurface.

Classification
Because bracket fungi are defined by their growth form rather than phylogeny, the group contains members of multiple clades. Although the term classically was reserved for polypores, molecular studies have revealed some odd relationships. The beefsteak fungus, a well-known bracket fungus, is actually a member of the agarics. Other examples of bracket fungi include the sulphur shelf, birch bracket, dryad's saddle, artist's conk, and turkey tail. The name polypores is often used for a group that includes many of the hard or leathery fungi, which often lack a stipe, growing straight out of wood. "Polypore" is derived from the Greek words poly, meaning "much" or "many", and poros, meaning "pore".

The group includes many different shapes and forms that are common in the tropical forests, including the hard 'cup fungi' and the 'shell', 'plate' and 'bracket' fungus commonly found growing off logs and still standing dead trees.

Description
The fungal individual that develops the fruit bodies that are identified as polypores resides in soil or wood as mycelium. Polypores are often restricted to either deciduous (angiosperm) or conifer (gymnosperm) host trees. Some species depend on a single tree genus (e.g. Piptoporus betulinus on birch, Perenniporia corticola on dipterocarps).

Forms of polypore fruit bodies range from mushroom-shaped to thin effused patches (crusts) that develop on dead wood. Perennial fruit bodies of some species growing on living trees can grow over 80 years old (e.g. Phellinus igniarius).Most species of polypores develop new, short-lived fruit bodies annually or several times every year. Abundant fruit takes place during the autumn or rainy season.

Structure of the fruit bodies is simple. Effused or resupinate fruit bodies typically consist of two layers - a tube layer of vertically arranged tubes that open downwards, and supporting layer called subiculum that supports and attached the tubes to substrate. In fruit bodies with a cap (pileate fruit bodies) the tissue between upper surface and the pore layer is called context. A few polypores (e.g. Fomes fomentarius and Inocutis rhaedes) also have a core between context and substrate. A minority of polypores also have a stalk (stipe) that attach to the cap either laterally or centrally depending on the species.

Polypore tubes are a honey-comb-like structure, where the individual tubes have fused together. Their sides are covered with a spore-forming surface, the hymenium. The tubes offer shelter for developing spores and help to increase the area of the spore-producing surface. Pore size and shape vary a lot between species, but little within a species – some Hexagonia spp. have 5 mm wide pores whereas pores of Antrodiella spp. are invisible to naked eye with 15 pores per mm. Generally the larger the pores, the larger the spores. A few polypores produce asexual spores (chlamydospores or conidia) in the upper surface of their cap (e.g. Echinopora aculeifera, Oligoporus ptychogaster) or without the presence of a sexual fruit body (e.g. Inonotus rickii, Heterobasidion spp.).
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