BRIEF DESCRIPTION:

The cap of A. mortenii is 35 - 75 mm wide, campanulate or conico-convex at first and subumbonate, eventually planar with or without distinct umbo, glabrous, tacky to dry, with a striate-sulcate margin. It is often olive-gray to olive-brown to predominantly olive-yellow at first with darker yellow-brown between striae. WIth time, the cap changes color significantly to ocher, ocher-brown, ocher-gray, or yellow-brown. The margin is often paler. The flesh is white, sometimes sordid yellow just below the cap skin, soft, and thin. The volva is absent or as small, pale saffron "flakes" or as pallid small patches with gray margins.

The gills are free to narrowly adnate, close, very pale buff to off-white in mass, becoming grayish with age. The short gills are truncate to subtruncate to subattenuate, of diverse lengths (often rather short), unevenly and sparsely distributed, occasionally adjoining stem rather than cap margin.

The stem is 62 - 140 x 6 - 17 mm, hollow, exannulate, with relatively broad central cylinder. The stem ranges from white to light gray; and it is palest toward the apex, becoming grayish or pale gray-brown near bruises and wounds. The flesh is white, becoming slightly grayish with age and rather brittle. The sac-like volva is submembranous, fleshy, flexible at first, then rather fragile; it is appressed to or adjoining the stem for about the lower third to half of the limb height.

The spores measure (8.5-) 9.5 - 13.0 (-17.0) x (7.2-) 8.5 - 11.5 (-15.0) µm and are globose to subglobose to broadly ellipsoid (infrequently ellipsoid) and inamyloid. Clamps are absent from bases of basidia.

This subarctic species tends to be more olivaceous at first, but becomes more orange on exposure and after collecting. Since the spore size also becomes slightly less globose at the same time, I was mistakenly under the impression for some time that there were two taxa. When Mr. Borgen took the lower of the two photographs a day after writing a description of the fresh material, my error was revealed. The most recent technical description of this species is by Tulloss and Borgen (1996). For comparison, see A. submembranacea (Bon) Gröger and the other taxa cited on that page. -- R. E. Tulloss