Bracket Fungi
Two examples of bracket fungi: Fomes and Ganoderma
If you are observant and spend much time hiking in the woods you are sure to encounter a bracket (shelf) fungus, fruiting bodies of wood decay fungi that are found both on standing and fallen trees and form a hard outgrowth with a spore producing surface facing downward. Unlike most mushrooms (gill fungi) that produce spores on linear rows (gills) (see Agaricus), these fungi produce spores in a tissue perforated with numerous cylindric pores, generally from 0.2 to 2 mm in diameter, through which the spores are shed. Fungi producing such structures are called polypore (‘many pores’) fungi, and while there are a few polypore fungi that do produce a ‘ mushroom’ shaped fruiting body, the majority of polypore fungi are bracket fungi, growing off trees trunks and branches like a shelf or a ‘bracket’.
Phylogeny
Both of the genera discussed here (Fomes and Ganoderma), and all fungi considered bracket fungi, are Basidiomycetes (club fungi) in the Kingdom Fungi. When fungal taxonomy was based on morphology (form) , all woody polypore fungi were lumped together, i.e. there was a taxonomic entity that included all woody polypore fungi. M ore recent analysis has revealed that woody polypores come from multiple lines, i.e. that a grouping of bracket fungi or of ‘polypore fungi’ is artificial, not phylogenetic.
Structure
Both of these fungi are typical fungi, producing colonial filaments of cells (hyphae) that branch and fuse to form a feeding structure called a mycelium. This branched dendritic form penetrates the heartwood of trees to obtain nutrition. As a result of certain stimuli the hyphae will grow in a very different way (highly condensed and intertwined) and in a different place (outside the tree stem) to produce a fruiting body, where special cells associated with sexual reproduction, are produced. The fruiting body of both these genera is described as being ‘trimictic’, meaning that it is composed of three different types of hyphae: generative hyphae, the ones that produce spores; skeletal hyphae, with very thick-walled hyphae and little branching; and binding hyphae, hyphae with extensive branching.
Sex and reproduction
Both of these fungi undergo the normal sexual process shown by basidiomycete fungi (‘club-fungi’). Haploid spores of two different mating types need to germinate on a tree and find each other to form a dikaryotic mycelium that feeds on the tree and grows. At some point a fruiting body is produced in which special cells undergo karyogamy to produce a diploid cell that immediately undergoes meiosis to form haploid basidiospores that are dispersed through the air to other trees.
Matter and energy
These fungi are typical heterotrophs that feed upon biomass produced by other living organisms. They are called ‘heart rot fungi’, feeding on the heartwood, the central cylinder of tree trunks that contains no living cells. Sapwood, the outer part of a wood, does contain some livi