Mycotaxon 15: 158-161. 1982.
Common Name: western grisette
Cap 8-18 cm broad, rounded at first, then convex, finally plane and slightly umbonate at maturity; surface viscid when moist; color dark brown, fading to light brown in age, occasionally with a remnant of universal veil tissue; margin conspicuously and deeply striate.
Gills adnexed to free, close white with brown edges.
Stipe 10-25 cm long, 1-3 cm thick, equal to narrower at the apex; pallid, covered with fine brown scales. Annulus absent. Universal veil forming a thick, membranous sac-like volva, sometimes developing rusty stains.
Spores 11.5-14.0 x 10-12 µm, smooth, nonamyloid, globose to subglobose. Spore print white.
Found commonly from mid-fall to mid-winter in mixed hardwood coniferous forest.
Edible but not choice.
Amanita pachycolea can be recognized by its large size, dark brown, deeply striate cap, absence of a ring, and well developed thick white, membranous volva. Its cousin, Amanita vaginata, is similar but smaller, has a cap which is not nearly so deeply striate, and is grayish rather than brown. Both species, however, can develop rusty stains on the volva.
Jenkins, David T. (1986). Amanita of North America. Mad River Press: Eureka, CA. 197 p.
Thiers, Harry D. (1982). The Agaricales (Gilled Fungi) of California. 1. Amanitaceae. Mad River Press: Eureka, CA. 53 p.
Thiers, H.D. & Ammirati, J.F. (1982). New species of Amanita from western North America. Mycotaxon 15: 155-166. (Protologue)