Fruiting bodies of Amanita sepiacea are medium-sized to large. The cap is 60 - 150 mm wide,
convex to applanate, dark grey to brown to blackish, darker in the center, innately fibrillose, covered with
dirty white to greyish (often brownish grey at the base) conical to verrucose warts, 1 - 4 mm high and wide; the
cap's margin is smooth and non-appendiculate; the cap's context is white.
The gills are free to subfree and white; the short gills are attenuate.
The stipe is 100 - 180 × 10 - 25 mm, subcylindric or attenuate upwards, with its surface
white to dirty white—its lower half covered with greyish to grey fibrillose squamules; the stipe's basal
bulb is 15 - 50 mm wide, subglobose to spindle-shaped to turnip-shaped, with its upper part covered with white, rarely
greyish, verrucose to conical volval remnants in a few concentric incomplete rings. The annulus is apical to
subapical, membranous, and white.
The spores measure (7.0-) 7.5 - 9.5 (-11.0) × (5.5-) 6.0 - 7.0 (-8.0) µm and are broadly
ellipsoid to ellipsoid, although occasionally subglobose
or globose and amyloid. Clamps are absent from the bases of basidia.
The species was originally described from Japan and occurs also in China.
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.
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.