Mycologia 95(3): 453. 2003.
Common Name: none
Synonym: Endoptychum depressum Singer & A.H. Smith
Fruitbody subhypogeous, then erumpent, cap 30-60 (90) mm broad, subglobose becoming convex to pulvinate, typically depressed at the disc; margin incurved, persistently attached to stipe; surface more or less glabrous, whitish, overlain with appressed brown fibrils, becoming, scaly to rimose in dry weather, yellowing slowly in age or with handling; pileus context relatively thin, up to 5 mm in width, firm to tough, cream to buff, yellowing where bruised or cut, at maturity, sometimes splitting exposing the spore bearing tissue; odor and taste of anise or almonds.
Gills reduced, consisting of anastomosing plates and convoluted chambers, maturing dark brown, eventually powdery.
Stipe 10-40 x 8-25 mm in width, subclavate, solid to hollow in old specimens; context firm, off-white to cream, yellowing like the cap; veil off-white to cream, membranous, relatively thick and tough, attached to the cap throughout development or pulling away in age exposing the spore bearing tissue; annulus absent.
Spores 6-8 x 5.5-7 µm, variable in shape: globose, subglobose to broadly ellipsoid, moderately thick-walled, lacking a germ pore, hilar appendage conspicuous; spores dark brown.
Solitary to occasionally in groups or clusters under montane conifers; fruiting from late summer through fall, rarely in the spring; uncommon in most years.
Probably edible based on relationship to members of the Section Arvensis; largely untried due to rarity. One of us (Wood) has tried it and found it good.
Agaricus inapertus is part of an adaptive trend seen in mushrooms of the Sierra Nevada i.e. fruiting bodies that tend to develop underground, or if above ground, with short stipes and in some cases with caps that don’t fully open, enclosing poorly developed gills that no longer forcibly discharging spores. Called secotioid development, these morphological characters are apparent adaptations to avoiding dessication. In the case of Agaricus inapertus, they were the taxonomic basis for early mycologists to place the species in the gastroid genus Endoptychum, thus the synonym E. depressum, even though the relationship to Agaricus was suspected and has since been confirmed. Agaricus inapertus is a mid to high elevation species found with a variety of conifers but is uncommon except in years with abundant rainfall. Often partially hypogeous, it is recognized by a typically short (occasionally specimens with normal stipes are seen), squat fruiting body that yellows slowly where handled, a faint anise odor, veil that often remains fused to the cap, and poorly formed (crumpled) gill tissue. Another secotioid Agaricus, A. deserticola, formerly known as Longula texensis, is fairly common in the Central Valley along edges of agricultural fields and waste areas. Also a member of the Section Arvenses, it is significantly larger, has a scalier cap, and fruits during the spring and fall.
Kerrigan, R.W. (2016). Agaricus of North America. New York Botanical Garden: Bronx, NY. 574 p.
Singer, R. & Smith, A.H. (1958). Studies on secotiaceous fungi II: Endoptychum depressum. Brittonia 10: 216-221. (Protologue)
Vellinga, E.C., de Kok, R.P.J. & Bruns, T.D. (2003). Phylogeny and taxonomy of Macrolepiota (Agaricaceae). Mycologia 95(3): 442-456.