Ganoderma applanatum, AKA the artist’s conk, is widespread through North America. These polypores are known for their white spore surface that turns brown with pressure, and many people (or nature lovers, including myself) have one hanging around the house as decoration.
Figure 1: Discolored, very old, decorated conk of Ganoderma applanatum from Southwest Virginia. The original owner (a mycophile) tried to preserve it using a stain and discolored the surface.
Ganoderma applanatum is a weak parasite/saprophyte, and can usually be found on dying or dead trees. They continue to grow and can get quite big, even up to 75cm (1).
The cap is typically shaped like a fan with a dull color. There are typically rings in the cap with the pore surface forming a ‘lip’ around the edge in younger conks.
The pore surface is typically white, and as it ages it becomes a more dull, brownish color (1). The underneath is a brown color, which comes out via ‘brusing’ which is how artists are able to ‘draw’ on the conks. The brown color of old brusing can stay crisp for years. They can turn black with KOH (1).
Figure 3: Two Ganoderma applanatum conks from Baker’s woodlot on Michigan State University’s campus. Note the brown fingerprints on the pore surface from when the collector had to yank super hard to remove the conk from the dead log it was residing on.
Spores are typically 8-12 x 6.5-8 µl, more or less elliptical with a truncated end. The spores appear smooth at lower magnifications. “but with oil immersion appearing double-walled, with a series of “pillars” between the walls (1).”
1. Kuo, M. 2004. Ganoderma applanatum. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/ganoderma_applanatum.html