Oak Crust

Peniophora quercina produces resupinate fruit bodies that vary in appearance depending on whether they are wet or dry. They are up to 0.5 mm (0.020 in) thick, and form irregular patches that sometimes measure several centimetres across. Initially, the species forms small, disc-shaped fruit bodies through holes in bark, but these expand and merge to form the irregular patches. When fresh, the surface is reminiscent of jelly or wax, and can be smooth or warty, varying in colour from a dull blue to lilac. Initially, they are firmly attached to the wood on which they are growing, but as they dry, the edges roll inwards and reveal the dark brown or black underside. The dry specimens have a crusty and slightly fissured surface, and, in colour, are a bright pink or grey, tinted with lilac. There is a relatively thick layer of gelatinous flesh. Apart from a brown layer close to the wood, the flesh is hyaline. The species has no distinctive odour or taste, and is inedible.

Microscopic features. Peniophora quercina produces spores that take the shape of a curved cylinder (sausage shaped), and have been variously reported as light red, pink and white. They measure from 8 to 12 by 3 to 4 micrometres (μm). The spores are borne on basidia, with four spores per basidium, which measure 50 to 70 by 5 to 12 μm. …

Peniophora quercina typically grows upon dead wood, which can be attached to the tree or fallen, where it causes white rot. It favours oak, but can also be found on other deciduous trees, such as beech. P. quercina is known to be a pioneer species on dead wood, which means it can be the first species to grow. It is found in Europe, where it is very common. Though it can be encountered all year, it produces spores in late summer and autumn. It has also been recorded in Amur, in eastern Asia. The species has also been identified in living sapwood, though it is latent at this time, and it is probable that it waits until the wood begins to die (when it is drier, but contains more oxygen) before the mycelia begin to grow. When the species was inoculated into living wood, it did grow, but only around the inoculation wound; the species did not spread as it would have done on dead wood. Another study found that the species actively colonised partially living branches, causing white rot. However, the species had little effect on the cambium, and was mostly limited to the ends of branches.

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