Amanita muscaria var. guessowii is the common,
bright yellow and/or yellow and orange fly agaric of eastern North America. The European name
A. muscaria var. formosa Pers. has been mistakenly
applied to this taxon. Some macroscopic dimensions in the
following are taken from (Jenkins, 1977).
Its cap is 45 - 180 mm wide. The pigment may wash out in rain or fail to develop under detritus if the latter covers a large part of the cap. The volva is distributed over the cap as cream to pale tan warts that tend to become somewhat sordid with age. The cap margin often becomes striate at maturity or in age. The context of the cap does not stain when cut or bruised.
The gills are narrowly adnate, subcrowded crowded mass and pale to cream in side view (with no observed staining or bruising reaction), with breadth 7.5 - 9+ mm. The short gills are truncate, unevenly
distributed, of diverse lengths, and plentiful.
The 60 - 150 × 6 - 21 mm stem (length includes a notable basal bulb) is white
to yellowish cream to pale yellow and annulate and usually narrows
upward and flares at the top. The stem surface is pulverulent
above the ring and coarsely shaggy to fibrillose and longitudinally
finely striate, below. The stem is stuffed in its 4+ mm
wide central cylinder with densely packed white material (fibers of
which have longitudinal orientation). Tunnels of insect larvae
through the flesh become yellow-brown. The ring is
membranous, persistent, skirt-like, and located on the upper part
of the stem; it may bear numerous warts from the internal limb
of the volva on the underside of its free edge. The upper side of
the ring is often not striate, and the underside is often
pulverulent. The basal bulb is subglobose to subovoid and 20±
× 21± mm. The lower stipe and upper bulb are decorated
with partial or complete rings of volval material as in
the type variety. The volval material ranges from bright pale yellow to
cream to sordid cream. Notice (for example, in some images above) that the
volval material on the stipe base may also take a form
reminiscent of the volva of species such as A.
pantherina (DC. : Fr.) Krombh., A. albocreata G. F. Atk.,
A. multisquamosa Peck,
or A. velatipes G. F. Atk.
The spores measure (7.0-) 8.7 - 12.2 (-14.8) × (5.9-) 6.5 - 8.2 (-9.5) µm and are
broadly ellipsoid to ellipsoid (infrequently subglobose
or elongate) and inamyloid. Clamps are present at bases of basidia.
This taxon can be found rather commonly in the boreal forests of eastern Canada (personally observed in Prov. Québec and on the Island of Newfoundland). Its range extends considerably further to the west and south. It is probably limited by the Great Plains of the central USA [the westernmost state cited in the variety''s range by Jenkins (1986) is Michigan]. The present taxon is known at least as far south as the central Applachian mountains (in North Carolina and Tennessee). Dried and annotated material from outside the above stated limits of distribution is very much desired by the author.
This variety apparently contains the same toxins as Amanita muscaria (L. : Fr.) Lam. subsp. muscaria of Europe, northern Asia, and far northwestern North America (western Alaska). With the recent large increase in immigration from Mexico into the eastern half of the U.S., we have seen an increase in poisonings by var. guessowii because it is mistaken for the edible Amanita basii Guzmán & Ramírez-Guillén (until recently, called "Amanita caesarea" by Mexican authors). When diagnosing the poisoning by questioning a Spanish-speaking victim, it is important not to simply translate "amarillo" as "yellow." One of the common names of Amanita basii in Mexico is "amarillo." A poisoning victim recently immigrated from Mexico to the eastern U.S. may be conveying the name of the mushroom by the word "amarillo," not just the color of it.
Amanita muscaria var. guessowii is associated primarily with conifers, but can occur with deciduous tree genera as well. It often occurs in the Fall in the mid-Atlantic states of the U.S., but it may appear as early as May in years with plentiful Spring rains. The northern limit of the range of this taxon is north of the Isl. of Labrador and central Quebec. The southern limit is not clear to me, but the range certainly includes the central Appalachian region. Other American taxa currently treated as varieties or subspecies of A. muscaria are A muscaria var. alba Peck, A. muscaria var. persicina Dav. T. Jenkins, and A. muscaria subsp. flavivolata Singer—R. E. Tulloss
≡Amanita muscaria var. formosa f. guessowii ("gussowii") (Veselý) Neville & Poumarat. 2002 ["2001"]. Bull. Trimestriel Soc. Mycol. France 117(4): 305. [Misapplication.]
=Venenarius muscarius sensu Murrill. 1913. Mycologia 5: 94, pl. 87 (fig. 3). [Misapplication.]
=Amanita muscaria sensu Güssow & O’dell. 1927. Mushr. Toadst.: 36, pl. 1 & 6. [Misapplication.]
=Amanita muscaria var. formosa sensu Dav. T. Jenkins. 1977. Biblioth. Mycol. 57: 53. [Misapplication. Amanita muscaria var. formosa Pers. is certainly not a North American taxon (Persoon said nothing to justify any such assumption) as proposed by Neville and Poumarat (2002, 2004), but more probably a color variant of the true A. muscaria.]
The editors of this site owe a great debt to Dr. Cornelis Bas
whose famous cigar box files of Amanita nomenclatural information
gathered over three or more decades were made available to RET for computerization
and make up the lion's share of the nomenclatural information presented on this site.
genetive of Latinized name, "Güssow's" or "of Güssow"
J. Geml et al. (2008), Molecular Microbial Ecology Lab., Univ. Alaska, Anchorage
[search for syntypes not completed]
Olive text indicates a specimen that has not been
thoroughly examined (for example, for microscopic details) and marks other places in the text
where data is missing or uncertain.
The following material not directly from the protolog of the present taxon is based upon
original research by R. E. Tulloss.
This description is obviously incomplete. Since recent studies suggest that this "taxon" may have to be reinterpreted as a cluster of genetically segregated yellow variants of Amanita amerimuscaria Tulloss & Geml nom. prov. (proposed new name based on A. muscaria subsp. flavivolvata Singer), it is suggested that readers interested in the probable microscopic anatomy of the "yellow variant" make reference to the reported microscopic characteristics of the just named taxon.
60 - 91 mm wide, margin yellow to pale yellow to orange-yellow with disk yellow-orange to orange to red-orange, sometimes entire pileus may be very pale if it is covered by detritus that protects it from sunlight, also decoloring in rain, hemispheric becoming convex then planoconvex and sometimes umbilicate, viscid when wet, tacky when drying, shiny when drying or dry; context ?, intense orange or yellow under pileipellis, fading to pale yellowish white in direction of lamellae, up to 10 mm thick over stipe, thinning evenly to margin; margin short striate (up to 0.2R), nonappendiculate; universal veil as warts or confluent warts irregularly distributed or approximately in concentric circles, subfloccose, pale yellow to pale sordid yellow fading to off-white to cream to sordid cream on exposure, detersile.
free to very narrowly adnate, sometimes with short decurrent line on stipe apex, subcrowded to crowded, cream in mass, white to pale cream to cream in side view, 7.5 - 9 mm broad, with edge minutely flocculose with white material except near margin of pileus where such material is yellowish; lamellulae truncate, unevenly distributed, of diverse lengths, plentiful.
69 - 120 × 10- - 15 mm, white to yellowish cream to pale yellow (in latter cases white at apex), becoming deeper yellow when handled, narrowing upward or narrowest at mid-height, flaring at apex, pulverulent above annulus, fibrillose to fibrous to squamulose and more or less longitudinally striatulate below; context pale yellowish white, unchanging when cut or bruised (unless senile?, then yellowing), solid to stuffed, with stuffing material comprising cottony white densely packed hyphae having roughly longitudinal orientation, with central cylinder 4± mm wide; bulb 20± × 20.5± mm, subglobose to subovoid to subventricose, often strikingly white, ?; partial veil whitish to very pale yellowish, thin, membranous, with thickened edge, median, pulverulent on upper surface, floccose on underside; universal veil in rings or broken rings on base of stipe above bulb, sometimes extending over several cm of stipe, sometimes more yellow than on pileus, fading and/or becoming sordid as on pileus.
Odor pleasantly fungoid. Taste not reported.
information not yet organized for presentation. (t.b.d.) POISON. Producing the Pantherine Syndrome in humans.
On pileus: filamentous, undifferentiated hyphae ?? µm wide, branching, ??, with many having yellowish subrefractive walls; inflated cells terminal (clavate to ellipsoid to ??, up to 114 × 56 µm) or intercalary (fusiform, up to 89 × 20 µm), singly or in short chains, with walls up to 1.5 µm thick, ??; vascular hyphae 3.0 - 14.0 µm wide, branching, scattered, ??; clamps present. On stipe base: ??.
In groups, often gregarious or in troops. Prov. Newfoundland and Labrador, Canada: In field, adjacent to forest edge with Picea glauca. Prov. Québec: In dry loam and duff of mixed forest including Betula, Pinus strobus, etc. New Jersey: Under Picea abies or Pinus spp. or under Tsuga canadensis or in mixed coniferous forest. North Carolina: On roadside under Picea engelmannii or under introduced Cedrus deodara. West Virginia: Under P. strobus or under P. resinosa.
CANADA: NEWFOUNDLAND & LABRADOR—Isl. of Newfoundland - Corner Brook, Humber Village Pond, 29.ix.2003 Maria & Andrus Voitk & R. E. Tulloss s.n. [Tulloss 9-29-03-A] (RET 270-7); GMNP, Killdevil Anglican Church Camp, tr. from camp to Lemona R, 15.ix.2004 Maria Voitk & R. E. Tulloss [Tulloss 9-15-04-A] (RET 383-3); Stanleyville, 13.ix.2004 R. E. Tulloss, M. & A. Voitk s.n. (RET 383-7, nrITS seq'd.).
QUÉBEC—Région Saugenay-Lac-Saint-Jean - Lac-Bouchette, L’Ermitage St. Antoine, behind Le Béthanie beside pedestrian tr., 31.viii.2006 R. E. Tulloss 8-31-06-B (RET 395-2).
U.S.A.: MAINE—Hancock Co. - Crocker Pond, 12.viii.1991 McVeigh s.n. [RET 8-12-91-B] (RET 031-4).
MASSACHUSETTS—Hampden Co. - Springfield, Forest Park, 28.vii.1986 Ellen Greer s.n. [Tulloss 7-28-86-EG5] (RET 466-8). Unkn. Co. - N of Boston, x.1987 Al Ferry s.n. [Tulloss 10-87-AF1] (RET 124-2, nrITS seq'd.). Unkn. Co. - unkn. loc., eastern part of state, 1991 member Boston Mycol. Club s.n. (RET 034-4).
MICHIGAN—McComb Co. - Shelby Twp., ca. Washington, Stony Brook Metropolitan Pk. [42.73° N/ 83.07° W, 250-260 m], 30-31.viii.2011 Sandy Sheine s.n. (RET 491-2). Washtenaw Co. - N of Dexter, Hudson Mills Metropark, 26.ix.1998 Heather Hallen Amus.980826.2 (MSU; RET 325-10).
NEW JERSEY—Burlington Co. - Brendan T. Byrne St. For., Pakim Pond picnic area [39°52’47” N/ 74°31’59” W, 33 m], 15.x.1995 Sarah, Mary, & R. E. Tulloss 10-15-95-A (RET 158-7, nrITS seq'd.). Camden Co. - Siklerville, 20.x.1998 19 mo. old female poisoning victim s.n. [Tulloss 10-20-98-A] (RET 289-1). Cape May Co. - Belleplain St. For., Jakes Landing Rd., E side of rd. ca. jct. with St. Rte. 47, 21.x.2006 R. E. Tulloss 10-21-06-J (RET 398-9); Woodbine, 29.x.1998 45 yr. old, male poisoning victim s.n. [Tulloss 10-29-98-A] (RET 289-3, nrITS seq'd.). Gloucester Co. - Glassboro, 14.x.1991 poisoning victim s.n. [Tulloss 10-14-91-B] (RET 034-1). Mercer Co. - Princeton, Princeton Unitarian-Universalist Congregation, 21.vi.2009 Mary A. Tulloss s.n. [Tulloss 6-21-09-A] (RET 429-1); Princeton Jct., 1.ix.1979 R. E. Tulloss 9-1-79-A (RET ??); West Windsor Twp., Village Rd. ca. Quaker Bridge Rd., 6.x.1980 R. E. Tulloss 10-6-80-A (RET ??), 16.ix.1981 Mary A. King & RET 9-16-81-D (RET 173-9). Monmouth Co. - Roosevelt, Pine Dr., sewer treatment plant [40°12’49”N/74°28’19”W], 6.x.1996 Mary A. Tulloss & R. E. Tulloss 9-6-96-B (RET 251-7); unkn. loc., 29.ix.1999 male Italian immigrant poisoning victim s.n. [Tulloss 9-29-99-E] (RET 303-4, nrITS seq'd.). Somerset Co. - South Plainfield, 17.ix.1997 Dorothy Smullen s.n. (RET 271-3, nrITS seq'd.). Sussex Co. - Stokes St. For., 25.vi.1983 Mary & R. E. Tulloss 6-25-83-C (RET 218-8); Stokes St. Pk., Kittle Field Recreation Area, 28.ix.1997 NJMA foray participants s.n. [Tulloss 9-28-97-C] (RET 271-2, nrITS seq'd.).
NORTH CAROLINA—Gaston Co. - Gaston Memorial Cemetery, ix.1995 Henry Rhyne s.n. (RET ??). Iredell Co. - 0.3 km N of Spring Shore Dr. on Pineville Rd., x.1995 A. Stanley s.n. (RET ??). McDowell Co. - Gooch Gap, along Blue Ridge Pkwy., 30.ix.2006 Pat & Owen Campbell & R. E. Tulloss s.n. [Tulloss 9-30-06-B] (RET 397-1).
PENNSYLVANIA—Allegheny Co. - North Park, 16.ix.2006 W. Penn. Mushr. Club foray participant s.n. [Tulloss 9-16-06-B] (RET 394-9).
OHIO—Butler Co. - ca. Oxford, Miami University Bachelor Wildlife Preserve, 7.xi.1992 Jeffrey Studer 23 (RET) & 26 (RET).
WEST VIRGINIA—Marion Co. - Fairmont, Fairmont St. Coll. campus, 30.x.1980(?) S. L. Stephenson 270 (FWVA), 13.ix.1982 Thais Salazar s.n. [S. L. Stephenson 601] (FWVA), 8.x.1982 Fred Tawny s.n. [S. L. Stephenson 603] (FWVA), 10.x.1982 Tom Asher s.n. [S. L. Stephenson 604] (FWVA).
Unkn. State—unkn. loc., x.1991 W. Bakaitis s.n. (RET).
This name is currently believed to apply to a group of yellow variants of Amanita muscaria subsp. flavivolvata, which, moreover, is not truly assignable to A. muscaria.
A phylogenetic study of the North American and Eurasian muscarioid taxa has appeared (Geml et al. 2008); allied taxonomic studies are in draft (by Tulloss, Geml, et al.).
—R. E. Tulloss
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RET - (1) Massachusetts, U.S.A.; (2-3) Gros Morne, National Park, Island of Newfoundland, Province of Newfoundland and Labrador, Canada; (4-5) New Jersey, U.S.A.; (6) northern border of Roosevelt, Monmouth County, New Jersey, U.S.A.; (7) Lac-Bouchette, Saugenay-Lac-St.-Jean, Province de Québec, Canada.
Each spore data set is intended to comprise a set of measurements from a single specimen made by a single observer;
and explanations prepared for this site talk about specimen-observer pairs associated with each data set.
Combining more data into a single data set is non-optimal because it obscures observer differences
(which may be valuable for instructional purposes, for example) and may obscure instances in which
a single collection inadvertently contains a mixture of taxa.