The following is based on the original description of Amanita xanthomargaros.
The cap of A. xanthomargaros is fuscous-brown to olivaceous brown, fuscous over the disc, yellowish near the margin, with innate, dark, radiating fibrils, 45 mm wide, plano-convex, dry, with a nonstriate margin. The cap is decorated with numerous, friable, soft, conical, umber-brown warts with yellow tips.
The gills are free, crowded, and white.
The stem is 55 × 3 - 8 mm, attenuate upward, solid, pale grayish brown, and yellowish at the apex. The flesh is white, becoming pale brownish or grayish-brownish on cutting, especially in the stem.
Spores from dried material measure 5.4 - 6.4 × 4.4 - 5.3 µm (from fresh material, 6 - 7 × 5 - 6 µm wide) and are subglobose to broadly ellipsoid and amyloid. Clamps were not observed at the bases of basidia.
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L (in liquid)
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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).
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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 is derived entirely from the protolog of the present taxon.
from protolog: ca. 45 mm wide, fuscous-brown to olivaceous-brown, fuscous over disc, yellowish near margin, with innate, dark radiating fibrils, plano-concave, dry; context white, sometimes becoming pale brownish or grayish-brownish on cutting, 3 mm thick above stipe; margin non-striate; universal veil as numerous, friable, soft, conical umber-brown warts with yellow tips, 1 - 1.5 × 1 - 2 mm.
from protolog: free, crowded, white, 5 mm broad, with white edge, 66 primaries; lamellulae attenuate, with 0 - 1 between each otherwise adjacent pair of lamellae.
from protolog: 55 × 3 mm (width measured at apex), narrowing upward, pale grayish brown, yellowish at apex, wholly lightly pruinose-cottony above and below partial veil; context solid, white, becoming pale brownish or grayish-brownish on cutting (especially noticeable in stipe); bulb clavate-submarginate, 8 mm wide; partial veil pendent, flaring, 3 mm measured radially from stipe to edge, membranous, mostly pale dingy yellow , deeper yellow at entire, smooth edge; universal veil as 2 - 3 powdery scurfy incomplete rings of confluent warts on stipe base and upper two-thirds [per figure] of bulb, with upper one fuscous and yellow, with others light yellow.
from protolog: Odor and taste not recorded.
from protolog: ca. 60 - 80 µm thick; suprapellis 10 - 20 µm thick, gelatinized, absent near margin; subpellis thickness not stated; filamentous hyphae brown, 2 - 4 µm wide in suprapellis (irregularly disposed, distant) and 4 - 10 µm wide in subpellis (rather crowded, irregularly to subradially oriented), near margin with elongate hair-like "crown cells," up to 180 × 15 µm.
from protolog: irregularly bilateral, loose; central stratum not distinct; filamentous hyphae present; inflated cells elongate and up to 135 × 30 µm in "central part," ellipsoid and up to 60 × 30 µm in "outer part."
from protolog: cellular (pseudoparenchymatous); 40 - 50 µm wide; inflated cells 10 - 25 µm wide, smaller near bases of basidia, larger and more ellipsoid near subhymenial base.
from protolog: 23 - 30 × 7.5 - 9 µm, 4-sterigmate; clamps not observed.
from protolog: On pileus: elements having more or less anticlinal orientation, especially in tips of warts; filamentous hyphae 2 - 7 µm wide, rather numerous; inflated cells dominating, globose to subglobose, 45 - 80 µm wide and brown in base of warts, 25 - 40 µm wide and yellow in tips of warts, terminal singly and abruptly for the most part, sometimes in short chains. On stipe base: filamentous hyphae 3 - 8 µm wide; inflated cells 20 - 50 µm wide, globose to subglobose, terminal singly or in chains, brown in uppermost ring, yellow in lower rings.
from protolog: longitudinally acrophysalidic; filamentous hyphae scattered, thin, loose, sometimes brownish on surface; acrophysalides up to 330 × 40 µm. [Note: There appears to be a typographical error in the text. It looks as if there was something "on" the stipe's brownish surface hyphae.—ed.]
lamella edge tissue
from protolog: inflated cells scarce in preserved material, colorless, up to 30 µm wide.
from protolog: [-/-/-] 5.4 - 6.4 × 4.4 - 5.3 μm, (Q = (1.05-) 1.10 - 1.30 (-1.35); Q = 1.20 - 1.25), hyaline, colorless, smooth, thin-walled, amyloid, subglobose to broadly ellipsoid, infrequently ellipsoid; apiculus proportionately small; contents monoguttulate; color in deposit not recorded.
from protolog: Solitary. Terrestrial in tropical forest.
from protolog: SINGAPORE: along Thompson Rd., 8.xi.1940 E. J. H. Corner s.n. (holotype, L in liquid, with watercolor drawing).
from protolog: "This species reminds one of the European A. franchetii (Boud.) Fayod (≡A. aspera ss. auct.), but the latter has a viscid, not fibrillosely streaked pileus, wholly yellowish warts, a whitish stipe, and larger spores, viz. 7.5 - 11 × 5.5 - 7 µm.
Amanita xanthomargaros is more closely related to A. pausiaca. These two species have in common (i) their habit, (ii) the olivaceous-brown, dry pileus, (iii) the yellow edge of the ring, (iv) the yellowish apex of the stipe, (v) the rows of small warts at the base of the stipe, and (vi) the small spores. However, in A. pausiaca, the remnants of the volva form grayish patches instead of yellow-tipped conical warts on the pileus, and fuscous-olivaceous warts at the base of the stipe instead of yellow ones. Moreover, the spores of A. pausiaca are slightly more globulose (average length-breadth ratio 1.1 - 1.15) than those of A. xanthomargaros (1.2 - 1.25). Nevertheless, these two species may turn out to be conspecific, if more material becomes available. "
In the protolog, it was suggested that the present species and A. pausiaca may prove to be conspecific when more material is available (Corner & Bas 1962: 271). Sporographs for the two taxa are compared in the following figure.
—R. E. Tulloss
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Corner & Bas
"Yellow Pearl Amanita"
1. Amanita xanthomargaros, Singapore.
2. Amanita xanthomargaros, Singapore.
Prof. E. J. H. Corner - (1-2) Singapore, illustration from original description (Corner & Bas, 1962) reproduced by courtesy of Persoonia, Leiden, the Netherlands.
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and explanations prepared for this site talk about specimen-observer pairs associated with each data set.
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a single collection inadvertently contains a mixture of taxa.