Original Description

BRIEF DESCRIPTION: The orange to brownish orange then reddish yellow cap of Amanita rubromarginata measures up to 80 mm wide and has a long sulcate-striate margin. The cap is at first cylindric-campanulate then expands to nearly plane to slightly concave and subumbonate. It is glabrous and subviscid when wet. The flesh is soft, 3 - 7 mm thick in the center, yellowish white, and deeper yellow below the cap skin.  

The gills are free, very close (55 - 70 reach the stipe), pale yellow and have reddish orange edges.  Short gills are of diverse lengths.

The stem is 60 - 120 × 5 - 16 mm, yellow, and has a thin, membranous, reddish orange annulus and and a thick, white, saccate volva. The stem is subcylindrical or slightly tapering upward, hollow, silky fibrillose, and appressed with indefinite, orange-red squamules forming irregular transverse zones.

The spores measure 8 - 9 × 5.5 - 7 μm and are broadly ellipsoid to ellipsoid and inamyloid. [Note: RET spore measurements from an isotype specimen are 7.5 - 9.5 (-10.5) × (5.8-) 5.9 - 6.9 (-7.6) μm, with spores dominantly ellipsoid, sometimes broadly ellipsoid, and rarely elongate.] Clamps are present at bases of basidia.

Amanita rubromarginata is easily distinguished from Amanita hemibapha (Berk. & Broome) Sacc. var. hemibapha [Ed. Note: In the present article, this must be taken sensu auct. japon.], Amanita hemibapha var.ochracea Zhu L.Yang, and Amanita javanica (Corner & Bas) T. Oda, C. Tanaka, & Tsuda by its smaller fruiting body, and its reddish orange annulus and reddish marginate gills.  [Ed. Note: Amanita rubromarginata is assignable to Amanita stirps Hemibapha, in the small-spored group (see key).  The spores of the present species are more narrrow than those of A. hemibapha sensu auct. japon. (=A. caesareoides Lyu. N. Vassilieva), the cap of which is brilliant red.  While A. hemibapha var. ochracea and A. javanica are similar to the present species in cap color, they both have larger spores and can be easily distinguished using the key on this site.]

Amanita rubromarginata was described from Oak-Chinkapin forests on Ishigaki Island (Okinawa, southwestern Japan). -- Dr. H. Takahashi

Photos: Dr. H. Takahashi

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Last changed 24 May 2006.
This page maintained by R. E. Tulloss.
Copyright 2005, 2006 by Rodham E. Tulloss.
Photographs copyright 2005 by Dr. H. Takahashi.