Observation 160898: Agaricus subrutilescens group

Pileus: Colored squamules over whitish undersurface; squamules vinaceous pink when fresh, dull dark brown when dry. Odor and taste mild, mushroomy, pleasant. Lamellae: pink to lilac to medium brown, not distinctly rufescent when cut.

Stipe: Somewhat fibrillose overall, giving way to thin white hoary layer over fibrils at base. When hoary layer rubbed away, orangish tan layer underneath revealed (a staining reaction?). Lower stipe is not cottony or shaggy. Base slightly bulbous, with a few rhizoids at the very base.

Annulus: upturned, subapical.

Staining – When cut: stipe mildly pinkish, no color change elsewhere. 10% KOH: very mild greenish reaction on pileus surface, yellowish to tan on stipe, except in inner hollow part, unreactive elsewhere, and unreactive anywhere in 5% KOH.

Cheilocystidia: absent, or at least none seen on lamella edge.

Spores: brownish, ellipsoid, no germ pore. Stats (n=7) – L: 4.9-5.8 (5.4 ± 0.35); W: 3.3-3.8 (3.5 ± 0.20); Q: 1.41-1.64 (1.52 ± 0.098).

Diagnosis: I’d call it Agaricus subrutilescens group, because that’s what it seems closest to. Nonetheless, it differs in several key features from what’s shown on Mykoweb and what’s described in Rick Kerrigan’s monograph:

  • Lower stipe not cottony/shaggy, but rather indistinctly fibrillose, with a a hoary covering. Seems to have a distinct color change when handled.
  • Lamellae not rufescent.
  • Pileus staining barely greenish, easy to miss.
  • Spore stats within range of variation described for this species, but somewhat larger than the average described by Kerrigan.

(Note – macro photos taken with cell phone camera, hence, the poor image quality.)


Basidiospores, bright field illumination, 100x objective. Zeiss AxioImager A1 + Axiocam MRc.
Lamella edge with basidioles; no noticeable cystidia. Phase contrast illumination, 40x objective. Zeiss AxioImager A1 + Axiocam MRc.
Pileus context and pellis hyphae, toluidine blue stain, bright field illumination, 2.5x objective. Zeiss AxioImager A1 + Axiocam MRc.
Detail of above image, 20x objective.

Proposed Names

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Used references: Mykoweb

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Add Comment
By: Peter G Werner (pgwerner)
2014-03-09 02:21:43 CDT (-0400)

It broadly fits A. subrutilescens, but with key differences outlined above. I will dry and save the collection – good thing it didn’t end up as a side to scrambled eggs, as originally intended. :-)

I’ll update the spore stats with a larger sample size next time I get on the microscope. The standard deviation was small enough even with the small sample size that I don’t expect any surprises there, however.

By: Byrain
2014-03-08 13:28:49 CST (-0500)

Start with spores & absence/presence of cheilocystidia, I’m not sure how helpful cystidia info would be here, spores can be helpful with Agaricus sometimes.

Microscopy of Agaricus
By: Peter G Werner (pgwerner)
2014-03-08 10:39:48 CST (-0500)

Actually, I don’t know much about the microscopy of Agaricus, and I seem to remember the spores are rather similar between species (though sizes might be different). What should I be looking for?

KOH the cap.
By: Debbie Viess (amanitarita)
2014-03-08 09:14:09 CST (-0500)

and I don’t have to tell YOU to scope it! ;)

subrutilescens usually has a shaggy stipe, altho that can get washed away.

when in doubt, send it to Fred!

Created: 2014-03-08 02:31:26 CST (-0500)
Last modified: 2014-03-09 03:50:36 CDT (-0400)
Viewed: 238 times, last viewed: 2017-12-25 18:40:33 CST (-0500)
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