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Species Information
Summary: Features include 1) a more or less spherical fruitbody with a thick rind-like skin that is not marbled in cross-section, the surface pale to dingy ochraceous, 2) a spore mass that is cottony to powdery, colored dark brown to black when mature, and 3) large spores that are round with short spines and are produced on asci, (Arora). It is often parasitized by Cordyceps, and may be the most common underground fruiting fungus in North America, (Smith(4)). It is abundant among truffles in the Pacific Northwest, but represents a species complex temporarily designated by a European name, none in the Pacific Northwest being identical with the European species (Trappe(13)).
Elaphomyces granulatus has been reported from BC in Redhead(5), from WA by Jumpponen(1), and from OR by Luoma(1) and Fogel(8). It is listed for ID by Hawker (in Fogel(7)), and reported from CO by Fogel(7). It has been found in the United Kingdom (Hawker(1)).
Outer Surface: 2-4cm across, spherical to nearly spherical, often with adhering strands of yellow mycelium; pale to dingy ochraceous, ornamented with firm coarse warts; peridium thick, firm, (Smith), 2-5cm across, "round to somewhat oval, very firm"; "sometimes pallid when young but usually pale to dingy ochraceous or yellow-brown"; exterior "usually covered with small hard warts (but these often hidden by a crust of soil, yellowish mycelium, and / or mycorrhizal rootlets)"; peridium [skin] rind-like, firm and thick (0.2-0.5cm) showing a very thin yellowish outer layer when sectioned, "and a thick white to grayish inner layer that may feature darker (brown) zones", but not marbled, (Arora)
Stem: none (Arora)
Interior: "dark brown to black and powdery at maturity", (Smith), "at first hollow, soon stuffed with cottony tissue, eventually becoming powdery when spores mature"; "white at first, soon grayish to purplish (and often separated into chambers by whitish bands), finally becoming blackish and powdery", (Arora)
Odor: not very distinctive (Arora), faintly metallic (Trappe, M.(3))
Microscopic: spores 28-45 microns in diameter, round, dark red-brown in KOH, with closely set short soft spines aggregated into irregular clusters; asci fleeting, (Smith), spores 24-45(65) microns, "round, thick-walled, blackish-brown to very dark reddish-brown under the microscope, ornamented with short spines or warts", asci "mostly 8-spored, round to pear-shaped, not forming a hymenium", and disintegrating before spores fully mature, (Arora), mature spores 23-32 microns in diameter with individual spines easily discernible and 2-4 microns long, immature spores (within asci) colorless with a distinctly radially striate epispore, (Hansen, L.)
Habitat / Range
scattered at or several centimeters below ground, "under conifers or hardwoods, summer or fall, widely distributed", (Smith), single, scattered or gregarious "in soil or humus under conifers or less commonly hardwoods", usually 5-8cm below surface, "often embedded in or resting on clay soil at point where it meets the humus layer", (Arora), year round (Bacon)
Similar Species
Elaphomyces asperulus has mature spores 25-38 microns in diameter, "individual spines scarcely discernible", "forming a cracking epispore" of 1 micron high, coalescent spines, immature spores colorless, with a very thin epispore, (Hansen, L.(1)). Elaphomyces muricatus is somewhat similar but its peridium is marbled in cross-section. Other non-marbled Elaphomyces are best distinguished microscopically. Scleroderma spp. usually have a distinct base or point of attachment, lack the small hard warts, usually grow closer to the surface or above it, and differ microscopically.
