Technical description (t.b.d.)

BRIEF DESCRIPTION: The cap of A. orsonii is 20 - 110 mm wide, , fleshy to fragile, globose to ovoid to convex when young, becoming broadly convex to plano-convex to plane with age, sometimes with a low, broad umbo, viscid to slightly viscid when wet, with a regular, decurved, nonstriate margin at first, becoming faintly striate with age. The cap is orange-red to grayish red to reddish brown to grayish brown, darker in the disc or having a light brown tinge in the disc, with color fading toward margin. The flesh is thin, white, staining reddish with age or injury, and soft. The volva is present as floccose, flat, polygonal scales and warts; it is white at first, grayish with maturity, and sometimes more plentiful near the margin than over the disc.

The gills are free to narrowly adnexed, close to crowded, white to yellowish white to grayish, staining red to grayish red in age or when bruised, thin, and fleshy to brittle. The short gills are sometimes rounded truncate, of diverse lengths, and unevenly distributed.

The stem is 35 - 150 x 8 - 30 mm, pallid with pink to red blotches to reddish white to grayish red to grayish brown, narrowing upward, pruinose at the apex, smooth to fibrillose, solid, becoming hollow with age, with white flesh. The volva is inconspicuous, friable, ephemeral or leaving few white to grayish white to grayish red to reddish brown patches adhering loosely to the bulb or in soil around the bulb.

The spores measure (6.5-) 7.0 - 9.2 (-10.5) x (5.0-) 5.5 - 7.0 (-8.0) µm and are amyloid and broadly ellipsoid to ellipsoid. Clamps are not observed at bases of basidia.

Amanita orsonii was originally described from the state of Himachal Pradesh in northern India. Its range is now known to extend from the Northwest Frontier Province of Pakistan to Japan (where it has been known as "A. rubescens").

It occurs with oaks and with conifers. The most recent detailed description is provided by Tulloss et al. (2001).

For comparisons, see Amanita rubescens (Pers.:Fr.) Pers.  

For distinguishing between rubescent taxa in section Validae, refer to the Key of rubescent taxa in Amanita section Validae. -- R. E. Tulloss

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Last changed 25 July 2006.
This page is maintained by R. E. Tulloss.
Copyright 2004, 2006 by Rodham E. Tulloss.