Amanita frostiana is a rather small species of the eastern U.S.A. and southeastern Canada—extending as far north as boreal forest on the Island of Newfoundland. With the exception of some localities, it is not commonly encountered; and the great majority of supposed collections of the present species are found to be wrongly determined material of Amanita flavoconia G. F. Atk. The latter species has ellipsoid, amyloid spores and no persistent collar of volval material at the top of the bulb.
The cap of A. frostiana is a yellow-orange or orange-yellow with the disc sometimes more red-orange than the rest and has a striate margin. The volva is distributed over the "20 - 80 mm" wide cap in yellow, friable warts.
The gills are free, close, and cream in mass. The short gills are truncate to excavated-truncate and plentiful.
The white stipe is "47- 62 × 4 - 11" mm (according to Jenkins' type study (1977), 94 × 6 mm in my only annotated collection) and bears a persistent ring. The distinct and starkly white bulb (e.g., 17 × 15 mm) bears a white or yellow-white collar that is somewhat similar to the collar seen in the exannulate Amanita albocreata G. F. Atk.
The spores measure (7.5-) 8.5 - 10.5 (-12.5) × (7.5-) 7.8 - 9.8 (-11.3) µm and are globose to subglobose (rarely broadly ellipsoid) and inamyloid. Clamps are present at bases of basidia.
This species is found in mixed forests with oaks (Quercus) and conifers (Pinaceae).
R. Heim reported A. frostiana from Thailand; however, his material is much more likely to have represented A. rubrovolvata S. Imai, a species lacking in clamps and, hence, not closely related to the present taxon.
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.
The field may contain magenta text presenting data from a type study
and/or revision of other original material cited in the protolog of the present taxon.
Macroscopic descriptions in magenta are a combination of data from the protolog and
additional observations made on the exiccata during revision of the cited original
The same field may also contain black text, which is data from a revision of the present
taxon (including non-type material and/or material not cited in the protolog).
Paragraphs of black text will be labeled if further subdivision of
this text is appropriate.
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 and not cited as the work of Dr. Z. L. Yang or another researcher is based upon original research by R. E. Tulloss.
54 mm wide, yellow orange, deeper orange over disk, planoconvex with decurved margin, tacky; context pale, cream near lamellae, yellow to pale yellow elsewhere except yellow orange under pileipellis, 6 mm thick at stipe, thinning evenly for about three quarters of radius, then membranous to margin; margin tuberculate striate (0.25R), nonappendiculate; universal veil yellow, small dissociating warts, pulverulent, minutely fibrillose (lens), detersile, not changing when cut or bruised.
free, without decurrent line on stipe, close, some crenulate, cream in mass, very pale cream to subtranslucent in side view, 8.5 mm broad, unchanging when cut or bruised; lamellulae truncate to excavate-truncate, plentiful.
94 × 6 mm, yellow except white just above the bulb, narrowing upward, then flaring at apex, finely pulverulent above, fibrillose to fibrous below, faintly longitudinally striate, unchanging when bruised; context cream, unchanging when bruised or cut, stuffed becoming hollow, with central cylinder 2 mm wide; bulb 17 × 15 mm, subglobose, somewhat flattened below; partial veil thin, membranous, yellow, sometimes collapsing and falling to inferior position; universal veil in a yellowish collar about 1 mm high completely circling top of bulb.
Odorless.Taste not recorded.
L-tyrosine test of tyrosinase: positive on stipe surface and in stipe context (only tissues tested). Syringaldazine test for laccase: negative on stipe surface and in context (only tissues tested). Test vouchers: Tulloss 8-16-85-B.
from type of A. macrospora: bilateral, divergent; clamps scattered.
from type of A. macrospora: pseudoparenchymatic (cellular).
from type of A. macrospora: ?? × ?? μm, dominantly immature, occasionally 1-spored, occasionally 4-spored (but with latter all lacking developing spores in section examined), with sterigmata sausage-like and up to 10.0 × 2.5 μm; clamps rather plentiful. [Note: This tissue is immature and the sterigmate are of abnormal shape.—ed.]
from type study of Jenkins (1978a): 7.9 - 8.7 × 7.9 - 8.7 μm, (Q = 1.0 - 1.01; Q' = 1.01), hyaline, smooth, thin-walled, nonamyloid, globose to subglobose; apiculus sublateral, truncate-conic; contents guttulate;
color in deposit not recorded.
[Note: The above report of perfectly spherical spores is probably an error. Creation of a sporograph is not possible without variation in Q value.—ed.]
from type of A. macrospora (RET): [28/1/1] (7.5-) 9.9 - 15.2 (-16.5) × (7.0-) 8.0 - 14.0 (-15.5) μm, (L = 12.3 μm; W = 10.4 μm; Q = 1.04 - 1.45 (-1.57); Q = 1.20), hyaline, colorless, smooth, thin-walled, inamyloid, globose to subglobose to broadly ellipsoid to ellipsoid, infrequently flask-shaped or lachrymoid, with many "giant" spores; apiculus sublateral, cylindric, often prominent; contents ??; white in deposit.
[Note: With most or all of the spores found on the type of A. macrospora coming from single-spored basidia, the large size of the spores could be predicted by assuming that the dimensions of the spores were increased by about the cube root of 4—since such spores would receive about 4× the content of a spore from a 4-spored basidium and, hence, have about 4× the volume of such a spore. The cube root of 4 is approximately 1.5874. Using the A. frostiana spore data, above, and hypothesizing that the type of A. macrospora is an immature specimen of A. frostiana producing "giant spores" from single-spored basidia, we can project the following "upper limit" data for A. macrospora: 95th-percentile of length = 16.7 μm; max. length = 19.8 μm; L = 14.6 μm; etc. We observe that these upper limits of spore size are not attained in the material examined; hence, the very large spores of the type of A. macrospora are well within the limits of the spore sizes that might be expected in case of spores from single-spored basidia actually had 4× the volume of spores from 4-spored basidia. In addition, 61% of the spores measured had a Q value within the range of Q for A. frostiana, below.—RET]
Spore data courtesy of Dr. Zhu-L. Yang: [199/10/6] (7.5-) 8.5 - 10.5 (-12.5) × (7.5-) 7.8 - 9.8 (-11.3) µm, (L = (8.5-) 9.0 - 9.6 µm;
L’ = 9.2 µm; W = (8.1-) 8.5 - 9.2 µm; W’ = 8.7 µm; Q = 1.0 - 1.12 (-1.17); Q = (1.04-) 1.05 - 1.08; Q’ = 1.06), hyaline, colorless, smooth, thin-walled, inamyloid, globose to subglobose to occasionally broadly ellipsoid, at least somewhat adaxially flattened; apiculus sublateral, cylindric; contents not recorded; white in deposit.
Gregarious or solitary in duff.
Newfoundland & Labrador: In boreal forest completely lacking Tsuga canadensis.
New Hampshire: In mixed woods with T. canadensis and Pinus sp. New York: In mixed forest including T. canadensis.
from type study of Jenkins (1978a):
U. S. A.: NEW YORK— Lewis Co. - Croghan,
s.d. C. H. Peck s.n. (neotype, NYS).
RET: CANADA: NEWFOUNDLAND & LABRADOR—Unkn. Co. -
Isl. Newfoundland, Gros Morne Nat. Pk., lower Green Gardens Tr., 5.ix.2003 Dr. Andrus Voitk s.n. (in herb. Dr. A. Voitk; RET 370-5).
NOVA SCOTIA—Kings Co. - Halfway River Rd., 27.ix.1966 H. Stewart 95 (holotype of A. macrospora, ACAD 10981).
ONTARIO—unkn. Co. - Port Dover [42.7863° N/ 80.198° W, 180m], 26.vi.2013 Eva Skific s.n. [mushroomobserver #137721] (RET 543-6, nrITS seq'd.), 6.vii.2013 E. Skific s.n. [mushroomobserver #138881] (RET 547-2, nrITS seq'd.).
U.S.A.: CONNECTICUT—Litchfield Co. - Washington Twp., N of Washington Depot, Bee Brook Pk., 25.vii.1992 Jackie Agnew s.n. [Tulloss 7-25-92-E] (RET 064-5). Windham Co. - Natchaug St. For., 31.viii.1997 Susan Hopkins s.n. [Tulloss 8-31-97-J] (RET 269-5).
MAINE—Cumberland Co. - Cumberland Center, 20-25.vii.1984 S. S. Ristich s.n. [Tulloss 7-20/25-84-SSR] (RET 238-1), 28.vii.1984 S. S. Ristich s.n. [Tulloss 7-28-84-SSR-B] (RET 238-3). Oxford Co. - unkn. loc., 2.vii.2012 James Veitch s.n. [mushroomobserver #99919] (RET 508-7). Washington Co. - Grand Lake Stream, Wabassus Lake [45.1572° N/ 67.8436° W, 87 m], 4.vii.2013 Teresa Clements s.n. [mushroomobserver #138672 (RET 546-2, nrITS seq'd.).
MASSACHUSETTS—Essex Co. - Boxford St. For., Peter Fechko, Rob Moir & R. E. Tulloss [Tulloss] 9-6-90-C (HKAS; RET 009-3). Unkn. Co. - unkn. loc., NEMF86 foray #15, 16.viii.1986 R. Youst s.n. [Tulloss 8-16-86-A] (RET 138-6). Unkn. Co. - unkn. loc., NEMF2001 foray #4, 17.viii.2001 Linda Clarke s.n. [Tulloss 8-17-01-A] (RET 362-1).
NEW HAMPSHIRE—Hillsborough Co. - SPNHF land, Swamp Rd., 18.viii.1989 Joe Kuczinski s.n. [Tulloss 8-18-89-A] (RET 246-9).
NEW YORK—Otswego Co. - Milford St. For., 16.viii.1985 R. Harlow s.n. [Tulloss 8-16-85-B] (RET 101-2). Oneida Co. - unkn. loc., 14.viii.2013 Eric Smith s.n. [mushrooomobserver #142718] (RET 588-6). Unkn. Co. - unkn. loc., 2013 E. Smith s.n. (RET 588-2, nrITS seq'd.).
VERMONT—Bennington Co. - ca. Bennington, Bennington Fish Culture Stn. [42°51'10" N/ 73°10'12" W, 288 m], 24.viii.1980 R. E. Tulloss & M. A. King [Tulloss 8-24-80-A] (RET 392-6).
—R. E. Tulloss
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1. Amanita frostiana, Milford St. For., Otswego Co., New York, U.S.A. (RET 101-2)
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.