Ischnoderma resinosum

Scientific name:  Ischnoderma resinosum (Schrad.)
P. Karst.
Derivation of name:  Iskhnos means "dry, withered,
or thin" and derma means "skin." Ischnoderma means
"with withered or wrinkled skin"; resinosum means
Synonymy:   Polyporus resinosus Fr.
Common names:   Resinous polypore.
Phylum:   Basidiomycota
Order:   Polyporales
Family:   Fomitopsidaceae
Occurrence on wood substrate: Saprobic; solitary or
grouped, sometimes in overlapping clusters on decaying
deciduous wood such as stumps and logs; September
through November.  
Dimensions:  Caps up to 25 cm wide and 2.5 cm thick.   
Upper surface:  Brownish-orange to dark brown,
becoming blackish; velvety when young, becoming glabrous
revealing thin, black zones of resinous crust; margin thick,
exuding amber-colored droplets when young.
Pore surface: Whitish, bruising brown; pores 4-6 per mm.
Edibility: Inedible.
Comments: The flesh of young specimens is soft and sappy
(juicy) at first.

More information at   

Figure 1. Ischnoderma resinosum growing on a Norway
maple (Acer platanoides). This picture was taken on
October 14. See Figure 2. Photo © Gary Emberger.

Figure 2. The same specimen of Ischnoderma resinosum
as in Figure 1 but photographed on November 7, three
weeks later. Photo © Gary Emberger.

Figure 3. Close-up of the specimen in Figure 2.
Photo © Gary Emberger.

Figure 4. Photographed in June the following year, this is
the tree suppporting the growth of Ischnoderma
in figures 1-3. It initially surprised me to find this
fungus growing on a living tree because all the references I
consulted indicate Ischnoderma resinosum is a
saprotroph. The apparent contradiction can be resolved by
noting that the tree is barely alive and due to the highly
compartmentalized nature of tree growth (and death),
most of this tree, including the portion where the fungus is
growing, consists of dead wood. Interestingly, then, the
fungus is growing as a saprotroph on a living tree.
Photo © Gary Emberger.

Figure 5. The species is fairly durable. These were found on
New Year's Day in South Central Pennsylvania.
Photo © Gary Emberger.

Figure 6. The surface may be concentrically and
radially furrowed and zonate. Photo © Gary Emberger.

Figure 7. In contrast to the specimens of Figures 5 and 6,
these are young specimens growing in the Fall. Note the
whitish growing margin. Photo © Gary Emberger.

Figure 8. Overlapping specimens growing on a log in
October. Photo © Gary Emberger.

Figure 9. Top surface (left) and pore surface of Ischnoderma
. Photo © Gary Emberger.

Figure 10. The brown bruising of the pore surface is
characteristic of this species. Photo © Gary Emberger.

Figure 11. When very young, Ischnoderma resinosum often
exudes droplets of moisture. Photo © Pam Kaminski.

Figure 12. The amber-colored droplets are only on the young
growing margin. Photo © Gary Emberger.


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