Amanita diemii : Diem's Amanita

Technical description (t.b.d.)

BRIEF DESCRIPTION

Amanita diemii has a cap 33 – 78 mm wide that is initially bright golden yellow to orange-ocher with the center yellow. Over time, the colors progressively darken through various tones to coffee or burnt umber with the margin always paler. It is convex at first, and often becomes depressed in the center or concave in age. It lacks an umbo, is always viscid, and often appears to bear fine scales or “areolate squamules” (sometimes teak colored) over the center (and sometimes with smaller squamules toward margin) — although the cap dries smooth. The cap’s flesh is largely white, yellow under pileipellis (at least at first), and unchanging when cut or bruised. The margin of the cap is short sulcate at first, then sulcate (to about one-quarter of the cap radius) or long pectinate, never uneven, often decorated with tooth-shaped fragments of volva. The volval remnants at first are found as broad rather flat patches (sometimes proportionately rather thick) that are white (occasionally drying pale grayish) and fibrillose-felted. Sometimes these patches break up into concentric appressed scales that can be removed. The skin of the cap is separable; but, in older specimens, it often ruptures into small scales in the region between the central area and the marginal striations. The latter is an unusual character in sect. Amanita.

The gills of this species are free, crowded to close, white, rather narrow, with edges that are often serrulate to crenulate or floccose-fimbriate; the short gills are truncate, infrequent(?), and unevenly distributed.

The stipe of A. diemii is 45 – 98 x 8 – 18 mm, white at first, eventually light cinnamon, at first narrowing upward, then becoming cylindric, densely flocculose-farinose to pruinose, and never glabrescent in age or even after heavy rain. The stipe’s bulb is usually distinct, 15 – 21 mm wide (14 – 21 x 10 – 17 mm and subglobose to subnapiform to napiform in dried specimens). The flesh of the stem is white, unchanging when cut or bruised, stuffed at first and later hollow. The annulus is often lacking and, when found, is very fragmentary and ephemeral, white, thin, and membranous. The volva is white, felted-membranous, rather thin, and appears as a circumcissile free limb [seeming ocreate–suggesting volva and bulb of A. pantherina (DC.:Fr.) Krombh. if free limb collapsed on stipe base] or as dentate sublimbate margin on the top of the bulb [suggesting the volva of A. gemmata (Fr.) Bertillon in Dechambre].

Amanita diemii has no odor and a mild taste.

The spores of this species measure (9.0-) 9.5- 11.5 (-12.8) x (7.5-) 8.2 – 10.2 (-11.5) µm and are subglobose to broadly ellipsoid (or infrequently globose) and inamyloid. Clamps are occasionally found at the bases of basidia.

Amanita diemii is found under Nothofagus in Argentina and Chile. If there is a very similar taxon (none are known, although perhaps the “pantherina-group” includes a candidate), that entity probably also occurs only in the Southern Hemisphere. Older specimens of this species have been misdetermined as A. umbrinella E. J. Gilbert & Cleland, which is an Australian taxon.

The species may be toxic and likely to produce symptoms similar to those of A. muscaria (L.:Fr.) Pers. and A. pantherina. — R. E. Tulloss

Photo: none available