Orange Sponge Polypore

The fruit bodies of P. alboluteus are annual, and are resupinate; they can be spread out on the substrate surface for up to 1 m (3+1⁄2 ft). Fresh fruit bodies are bright orange, finely grooved, and have a soft and spongy upper surface. The pore surface is orange with angular pores that are usually larger than 1 mm in diameter. It features thin partitions that split to form a teeth-like layer. The flesh is soft and pale orange, up to 2 mm thick, with a felt-like texture. The tubes are the same color as the pores, and continuous with the flesh, measuring up to 2 cm (3⁄4 in) thick. Bruised pores sometimes turn black. All tissues of the fungus turn bright red if a drop of dilute potassium hydroxide is applied. Fresh fruit bodies retain considerable moisture and can be squeezed of liquid like a sponge. The fruit body can be readily removed in large sheets from the wood it grows on. The edibility of the fruit body is unknown. It has a fragrant odor.

In deposit, the spores are white. The spores are cylindrical, smooth, hyaline (translucent), inamyloid, and measure 9–12 by 3–3.5 μm. Pycnoporellus alboluteus has a monomitic hyphal system, meaning it is made of generative hyphae, which are thin-walled, branched, and narrow. …

Pycnoporellus alboluteus causes a brown cubical rot on fallen logs of coniferous trees. The fruit bodies usually grow on the underside of the log, and may start developing while still immersed in snow. Although new fruit bodies usually begin growing in the spring, they may persist throughout the year. In Europe, it usually grows on Picea species, but also on Abies. In North America, it also grows on Populus. The fungus has a circumpolar distribution, and is found in the boreal conifer zone, particularly in the montane zone, 2,400–3,000 m (8,000–10,000 ft). In North America, the fruit bodies begin growth under snow in the spring, continuing until midsummer, while in Europe, it is usually encountered in autumn. It is abundant in the Rocky Mountain region of North America, but rare in the eastern United States and Canada. As a timberline fungus subject to high altitudes, the fruit bodies are subjected to bright light, high winds, and low relative humidity, all of which have a drying effect. They counteract these extremes by absorbing water quickly, and drying slowly. In Europe, it is one of 32 threatened species proposed for protection under the Bern Convention. It has been recorded from Czechoslovakia, and Poland, where it is mostly found in old-growth forests. …