Veiled Polypore

The Veiled Polypore (Cryptoporus volvatus) is one of the most unmistakable bracket fungi in the world, because it does not look like a bracket at all. Instead of an exposed pore surface facing the ground, the entire tube layer is enclosed within a tough membranous veil that seals the underside, leaving only a single small round opening near the point of attachment. The result is a smooth, pale, glossy pouch clinging to the trunk of a dead conifer, closer in appearance to a small puffball or a gall than to a polypore.

The genus name means hidden pore, and Cryptoporus contains only a couple of species worldwide. The enclosed chamber is a genuine evolutionary innovation: spores are shed into a protected cavity and leave through the single hole, largely carried out on the bodies of insects that crawl in and out.

It is closely tied to bark beetle activity and appears in enormous numbers in the year following an outbreak or a fire, when large areas of standing conifer are freshly killed. In such stands, hundreds of pale globes can dot a single trunk.

Fruiting body

Small, hard and rounded, 2-6 cm across and 1.5-4 cm thick, shaped like a flattened globe, kidney or short hoof, attached to the bark by a narrow point or broad base. The upper surface is smooth, glossy and slightly leathery to varnished in texture, coloured cream, pale tan or buff, darkening to ochre or reddish brown with age. Old specimens crack and weather greyish.

Veil and pores

The entire underside is covered by a tough, smooth, pale membrane continuous with the cap surface, so no pores are visible externally. Near the base of the veil is a single small round to oval opening, typically 2-6 mm across, which develops as the fruit body matures. Cutting the fruit body open reveals a hollow chamber above which the true pore surface hangs: white to pale buff, with small round pores about 3-5 per millimetre, ageing brownish.

Flesh and spore print

The flesh is thin, tough, corky and white to pale buff, drying hard and light. The whole fruit body becomes remarkably lightweight when dry. The spore print is white, although obtaining one requires opening the veil since spores are released into the internal chamber rather than into open air.

The Veiled Polypore fruits on standing dead and very recently killed conifers, above all pines, but also Douglas-fir, spruce, larch and true firs. It grows through the bark of trees that died within roughly the previous one to three years, and it is strongly associated with trunks attacked by bark beetles and with fire-killed timber. It seldom appears on long-dead or debarked wood.

It is common across the conifer forests of western and to a lesser extent eastern North America and occurs in eastern Asia. Fruit bodies typically form in spring and early summer, but because they are hard and weather-resistant they remain attached to the trunk for a year or more and can be found in any season, gradually weathering grey.

Cryptoporus volvatus is a white-rot saprotroph of conifer sapwood, colonising trees almost immediately after death. Its spores are carried to fresh wounds by bark beetles and other insects, so its arrival is often simultaneous with the beetle attack that kills the tree.

The enclosed veil creates a humid, sheltered chamber in which spores accumulate. Beetles, flies and other small insects enter through the single opening, become dusted with spores, and carry them onward to newly killed trees, making this one of the clearest cases of insect-mediated spore dispersal among the polypores. The fungus is therefore an early and important initiator of decay in beetle-killed and fire-killed conifer stands, beginning the breakdown of standing dead timber that will eventually become snag habitat and downed wood.

No other North American polypore encloses its pore surface in a veil, so a fresh specimen is effectively unmistakable. The confusion, when it happens, is with fungi that are not polypores at all: small hard puffballs and Scleroderma earthballs are similarly globose but grow on soil rather than on standing bark and are filled with a spore mass rather than being hollow above a pore layer.

Young, unexpanded knobs of Fomitopsis pinicola and Ganoderma species on the same conifer trunks can be rounded and pale, but they have a visible, open, cream pore surface from an early stage and go on to expand into shelving brackets rather than remaining sealed globes. Old weathered Cryptoporus fruit bodies with a broken veil can look like small hoof-shaped brackets, but the ragged remnant of the membrane and the hollow chamber inside remain diagnostic when the specimen is cut in half.