Summary:
Subgenus Vaginatae. Amanita pachycolea is characterized by tall slender stature; broad dark brown to dark gray brown cap that is markedly striate; characteristic gill color with dark margins; white to bright brown stem; absence of partial veil and ring; and a huge sheathing volva at the base of the stem with ferruginous stains. |The holotype is from California but the original description cited also three collections from Washington as well as other Californian collections. |According to D. Miller, pers. comm., there are more than one species covered by the name. |The term ''grisette'' refers to Amanitas with tall, slender stature, striate cap margin, and saccate (or constricted saccate) volva, but without a partial veil or annulus. Which of the grisettes occur in the Pacific Northwest is uncertain although they are common as a group. |A. pachycolea, Amanita vaginata (and presumably the fulvous colored Amanita that resembles A. vaginata), and Amanita ''alba'' differ from A. constricta in that the volva is attached only at the bottom of the stem while in A. constricta the volva is firmly attached partway up the stem and flares open at the top. |The Amanita ceciliae group also has a constricted volva. There is also a species or group of species designated "NW 4" in Lindgren(1) that keys out close to A. pachycolea but has pale tan to light brown cap, and the volva may be constricted. |Thiers(5) say that A. pachycolea is often rather common in the north coastal forests of western North America.

Cap:
7-12(20)cm across, at first oval then convex and finally flat with an umbo, or with an upturned margin; "dark brown, shading lighter toward the margin and with a darker band at inner edge of striations"; viscid when moist, smooth, (usually) without a patch or warts of universal veil, margin deeply striate, (Lindgren), 7-20(25)cm across, at first oval then convex or somewhat bell-shaped and finally flat or with an upturned margin and often a low, broad umbo; "dark brown when young, brown to grayish-brown or paler in age (usually darker at the center and paler toward margin or with a darker brown band at inner edge of the striations)", sometimes completely washed out when old; viscid when moist, smooth, occasionally with a thick patch or patches of universal veil, margin deeply striate-grooved from 1.5-3cm, (Arora), 7-12cm across, convex to near bell-shaped when young, becoming convex to flat-convex to umbonate to sometimes irregular in outline with a wavy margin when old, margin decurved [downcurved], unchanging or becoming flat to uplifted when old; 'dark brown, "carob brown" to "chestnut brown" to "mummy brown" on the disc, fading toward the margin to brown or grayish brown, "hazel" to "sayal brown" to "tawny olive", sometimes with a noticeable dark ring of brown pigment at inner margin of striations'; viscid to subviscid, bald except for occasional scattered fibrils, "rarely with a flat, usually solitary patch of white to whitish universal veil on the disc", margin typically becoming rimose [cracked] and eroded, conspicuously striate or tuberculate-striate, striations 1.5-2cm long, the noticeable band of abruptly ending striations of equal length remaining distinct when dried, (Thiers)

Flesh:
soft; white, (Lindgren), rather soft; white, (Arora), 0.5-1cm thick on disc, thinner toward margin, floccose; white, unchanging when bruised or exposed, (Thiers)

Gills:
close, broad; white, discoloring orangish when old, edges fringed and usually dark brown, (Lindgren), adnate becoming adnexed or free, close, broad; white with dark brown edges when fresh, sometimes discoloring dingy orange or yellow-orange when old, (Arora), "adnate to decurrent by a short, inconspicuous hook", typically free when old, close to subdistant or occasionally appearing crowded, subgills in several tiers, gills broad, ventricose; "white when young, unchanging or becoming tawny to orange brown or orange yellow with age, sometimes with only spots showing these colors, usually drying yellow to buff", gill edges usually colored grayish to slightly drab or dark brown; edges fimbriate [fringed], (Thiers)

Stem:
12-30cm or more long, 1-3cm wide, equal or widening downward, hollow when old; "covered with gray-brown to brown fibrillose scales on a pale background", (Lindgren), 12-30cm or more long, 1-3cm wide, equal or widening gradually downward, hollow or stuffed when old; pallid with fine delicate grayish brown to brownish particles or fibrillose scales, (Arora), 11-24cm x 0.9-1.7cm, equal to widening, often slightly, downwards, no bulb at base, stuffed becoming hollow when old; white to olive buff to sometimes as dark as orange brown or darker; dry, typically appressed-fibrillose to fibrillose-scaly, sometimes only slightly furfuraceous at top, (Thiers), VOLVA membranous, thick, saccate, tall, white with rust colored stains, (Lindgren), membranous universal veil, forming a very large loose lobed sac-like volva at base of stem for up to 12cm, but attached only at base, ample, thick, white or rusty-stained, (Arora), "abundant, saccate, thick and felted", persistent but sometimes collapsing when old, frequently extending as high as 8cm up the stem and up to 0.5cm thick, "inner surface white, outer surface white to off white, usually developing rust colored to brown or yellow brown spots with age, sometimes becoming entirely ferruginous or dingy yellowish white", (Thiers)

Veil:
ring absent (Lindgren, Arora, Thiers)

Odor:
mild(Lindgren), sometimes unpleasant when old (Arora), not distinctive (Thiers)

Taste:
mild(Lindgren), mild, may be fishy when old, (Arora), not distinctive (Thiers)

Microscopic spores:
spores 11-14.5 x 10-12.5 microns, broadly elliptic to round, inamyloid, (Lindgren), spores 11-14.5 x 10-12.5 microns, broadly elliptic to round, smooth, inamyloid, (Arora), spores 11.4-13.5(14.4) x 10.4-12.4 microns, round to oval, smooth, inamyloid, thin-walled, colorless in KOH, apiculus eccentric or nearly so; basidia 4-spored, 53-80 x 13-16 microns, clavate, colorless in KOH; pleurocystidia and cheilocystidia not differentiated, marginal cells of gills abundant to sometimes apparently absent, 20-27 x 6-17 microns, clavate, terminal, colorless in KOH, not in chains; clamp connections absent, (Thiers)

Spore deposit:
white (Thiers)

Notes:
Thiers(5) studied collections from WA and CA. Collections from BC by Paul Kroeger are deposited at University of British Columbia, and there are collections from OR at Oregon State University labeled as this species.

EDIBILITY

yes but be sure of identification, not choice, (Lindgren, Arora)