Ischnoderma resinosum

[ Basidiomycetes > Polyporales > Hapalopilaceae > Ischnoderma . . . ]

by Michael Kuo

This attractive and widely distributed polypore is easy to recognize--with close inspection. The young mushrooms are thick, soft, and fleshy--much softer than you might expect in a polypore, especially if, from a distance, you thought you were looking at Ganoderma applanatum. The young pore surface is whitish, but it turns brown very quickly when bruised. Ischnoderma resinosum has a tendency to grow not only on the sides of dead logs, but also on their undersides, where it produces a capless version (or extension) of itself that consists primarily of a pore surface (see the fourth illustration). As Ischnoderma resinosum matures, it becomes very tough and leathery, and much more "polyporeish."

Description:

Ecology: Alone or gregariously on fallen hardwood and conifer trunks and branches; sometimes in overlapping clusters; annual; saprobic; causing a whitish to yellowish rot that separates the annual rings in the wood and often smells of anise; appearing on recently fallen wood and on wood that has been down for many years, but not typically on well rotted wood; usually a fall species, in north-temperate regions; very widely distributed in North America.

Fruitbody: Up to 15+ cm across; irregularly bracket-shaped or kidney-shaped; broadly convex; when young quite thick and fleshy, with a pale brownish, finely velvety cap surface and a thick white margin that can be adorned with water droplets in wet weather; in maturity dark brown, sometimes with zones of color, fairly smooth, dry, tough and leathery or corky; without a stem.

Pore Surface: When young whitish, soft, promptly bruising brown; in maturity pale brown and hard; 4-6 angular or round pores per mm; tubes to 1 cm deep.

Flesh: Whitish and soft at first; darkening to brownish or cinnamon brown, and becoming tougher with maturity.

Chemical Reactions: All parts grayish to blackish with KOH.

Spore Print: White.

Microscopic Features: Spores 5-7 x 1.5-2 µ; smooth; cylindrical (if sectioning for spores, use the marginal area of young specimens); clamp connections present.

REFERENCES: (Fries) Karsten, 1879. (Overholts, 1953; Smith, Smith & Weber, 1981; Gilbertson & Ryvarden, 1986; Arora, 1986; Phillips, 1991/2005; Lincoff, 1992; Barron, 1999; Roody, 2003.) Herb. Kuo 09220407, 10070401.

Polyporus resinosus is a former name.

"Ischnoderma benzoinus" is recognized as a separate, conifers-only species by some authors (especially in Europe), who separate it from a hardwoods-only Ischnoderma resinosum on the basis of its putatively darker flesh. Culture studies refute this separation, however, and the reigning authoritative source on North American polypores (Gilbertson & Ryvarden, 1986) synonymizes the two species--as did the previous North American polypore "Bible" (Overholts, 1953).

Further Online Information:

Ischnoderma resinosum at Roger's Mushrooms
Ischnoderma resinosum at Fungi of Poland

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Cite this page as:

Kuo, M. (2004, October). Ischnoderma resinosum. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/ischnoderma_resinosum.html