BRIEF DESCRIPTION: Amanita xylinivolva is a locally common species with a range extending from Andean Colombia to the "mountain islands" in high desert of the southwestern Arizona, U.S.A.

Its 15 - 70 mm wide cap is pale yellow and becomes paler (except sometimes for the central part) with aging.  The volva is either absent from the cap or distributed on the cap as cottony white patches that sometimes become sordid with age.

The gills are free to narrowly adnate, subdistant to crowded, whitish to cream to pale buff in mass, and sordid white (sometimes with yellow tint) in side view.  The short gills are truncate to subtruncate to attenuate.

The stipe is 45 - 135 x 4 - 13 mm, quickly loses its fragile skirt-like annulus, and usually has a cottony white, submembranous limb of volva on the top of a rather prominent bulb (10 - 25 x 15 - 30 mm).

The spores measure (6.2-) 8.0 - 10.2 (-12.2) x (5.2-) 7.2 - 9.5 (-10.8) µm and are globose to subglobose to broadly ellipsoid (infrequently ellipsoid and inamyloid.  Clamps have not been found on bases of basidia.

Between the above cited extremes of its geographic range, this species has also been collected in Costa Rica and central Mexico.  The species is associated primarily with oak (Quercus) and pine (Pinus). -- R. E. Tulloss