Summary:
Features include saddle-shaped to 2-lobed or irregularly lobed cap that is red-brown to dark red brown, most often with violet tints, with edge curved down on one horizontal axis and up on the horizontal axis at right angles, and both fused to itself (to form the saddle) and fused to stem, white to cream or light red-brown downy underside, pale pinkish cream to purple brown downy stem that often has violaceous tints, the stem round in cross-section or fluted at base, growth under conifers (especially pine) or on conifer wood, and somewhat spindle-shaped spores with two droplets and distinct or indistinct apiculi. Gyromitra species can be very poisonous when eaten raw, although toxicity varies with the individual, and certain individuals who have eaten Gyromitra mushrooms without effect have had severe reactions on another exposure. In a 1967 report of 513 cases of this kind of poisoning, 14% were fatal. Gyromitra ambigua is probably like Gyromitra esculenta in containing gyromitrin (and other hydrazones), which is metabolized to what appears to be the major toxin, monomethylhydrazine (that has been used as a rocket fuel). Much but not all of this becomes a vapor during cooking and can be poisonous as vapor. Poisoning starts between 2 and 24 hours and may start with vomiting, diarrhea, abdominal pain and headache. Sometimes there is fever. Liver toxicity occurs about 36-48 hours, and then neurological symptoms including seizures and coma. Sometimes there is intravascular hemolysis, kidney failure, or methemoglobinemia. With lower doses, there is still concern that these mushrooms are carcinogenic. (Benjamin, from "Gyromitra species"),

Odor:
not distinctive (Phillips), not distinct (Harmaja(6))

Taste:
mild (Phillips)

Microscopic:
spores 21.4-30.0 x 7.7-11.2 microns, typically subfusoid, sometimes elliptic and fusoid spores also present, smooth, with two droplets, very rarely with 1 or 3 droplets, distinctly or indistinctly apiculate, apiculi 1-2 microns long, broadly rounded, (Abbott), spores 22.0-33.0(37.5) x 7.5-12.0 microns (excluding the perispore 20.0-29.0 (34.5) microns long), "subfusiform to broadly fusiform, inequilateral", smooth, colorless in KOH, yellowish in Melzer''s reagent, "perispore surrounds the spore, but it is usually observable only at the apices where it is inflated and off from the spore wall forming an appendage of varying breadth" (1.5-3.0 microns), perispore plasma deeply staining in cotton blue, spore rather thick-walled (about 0.5-0.6 microns), with 2 large droplets, mostly 1-seriate; asci 8-spored, 210-280 x 10-20 microns; paraphyses +/- straight, very thin-walled, occasionally branching in lower part, septate, clavate to subcapitate, +/- gradually expanding to tip which is 10 microns wide at most, encrusted and intracellular pigments exactly as in G. infula, (Harmaja), spores 22-33 x 7.5-12 microns, subfusiform to broadly fusiform, with 2 large oil droplets, (Phillips)

Notes:
G. ambigua collections examined from WA, AB, MB, PQ, SK, YT, AK, Finland, distribution also includes BC, and reported from MT, eastern North America, Europe, and Asia, (Abbott), NJ (Phillips)

EDIBILITY

poisonous (Harmaja(8), who discusses a case in which the consumption of the water used in boiling along with the mushroom apparently was associated with a poisonous reaction)

Synonyms and Alternate Names:
Merulius molluscus Fr.
Merulius subaurantiacus Peck