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Species Information
Summary: Also listed in Truffles etc. category. Montagnea arenaria is at first deeply buried and enclosed in a tough membrane, then expands as the ruptured outer skin forms a volva at the base of the stem. The mature fruiting body has a stem and a cap (all but the cap disc (cap center) soon splitting into spore-bearing plates). The online Species Fungorum, accessed December 15, 2015, gave the name as Montagnea arenaria (DC.) Zeller as above, and it would seem that the Latin word ''arenarius'' meaning ''sandy'' should agree with the ending of the genus named after Montagne, but Zeller called it Montagnea arenarius when combining the name in 1943. The description is derived from Arora(1).
Arora(1) mentions distribution in the arid and semi-arid parts of western North America (from Mexico and TX to CA, OR, and eastern WA). Collections were examined from OR, AZ, NM, Texas, Mexico, Russia, and Algeria, (Zeller). There are collections at the University of British Columbia from BC, AZ, CA, and NM. There are collections at the College of Idaho from ID and Mexico.
Cap: 1-3.5cm across, merely a thin disc-like expansion of the stem, convex becoming flat or depressed, persistent, all but the disc soon splitting into spore-bearing plates; "white to grayish, buff, or occasionally straw-colored"; surface smooth, often with a volval patch or remnants, margin often tattered or fringed when old
Flesh: in stem white when fresh
Gills: spore mass exposed at maturity, composed of thin plates that radiate or hang from the margin of the disc-like cap and are entirely free from stem, plates often wavy or curled up, up to 3.5(6)cm long, reddish-black to blackish when mature, eventually falling off the cap or disintegrating but not deliquescing
Stem: (5)8-30cm x 0.2-1.5(2.5)cm, percurrent [going through cap], more or less equal or often narrowing downward, "hollow, tough or almost woody when old and dry (but very light)", white to buff or sometimes discoloring darker when old; "smooth or longitudinally fibrillose-striate, often splitting or cracking into fibrillose or shaggy scales", volva at base of stem sac-like, "usually buried in soil, loose (often remaining in ground), two-layered, the outer layer white and ample, the inner layer composed of tough fibers"
Veil: absent or rudimentary
Microscopic spores: spores (7.5)12-20(28) x (4.5)6-11(14) microns, elliptic to nearly round, smooth, with germ pore, capillitium absent
Spore deposit: print not obtainable
Habitat / Range
single, scattered or gregarious "in sandy soil, old fields, and other waste places", in arid and semi-arid areas
Similar Species
Gyrophragmium californicum is similar but rarer, (known from the San Francisco Bay area in California), and has dark brown to blackish spore-bearing plates that hang from the underside of the disc-like cap rather than from the margin. It also has a loose volva plus a double-layered partial veil that either disappears or forms an annulus (ring). (Arora(1)). A Gyrophragmium species has been reported from Washington state, (Lorelei Norvell, pers. comm.): instead of having spore bearing plates that hang from the edge of the cap, the plates hang from the underside of the cap.
