Agaricus placomyces

     Agaricus praeclaresquamosus
     Agaricus pocillator
     Agaricus meleagris

Cortinarius husseyiKey to Gilled Mushrooms     Key
This is a key to gilled mushrooms, that is, mushrooms having a definite cap with a fertile surface consisting of gills. The fruiting body usually also has a stem, although that may be lateral or absent (usually, then, the mushroom is growing from wood). You can use this key to identify mushrooms that you find.

TricholomaAgaricales     Order
Fruiting body containing fibers (usually in the stalk)

Agaricus campestrisAgaricus     Genus
Gills free
Spore print chocolate brown
Annulus almost always present, usually membranous
The gills are usually pink or silvery-grey at first, but are colored chocolate brown at maturity from the developing spores
The cap and stalk are usually some sort of white or greyish brown, but may have fibrils or scales that are darker (like the portobello)
Growing on the ground, wood chips, or other organic debris

Xanthodermati     Section
Flesh at the base of the stalk staining yellow when cut
Odor phenolic (sometimes faintly)
Flesh turning yellow in KOH

Agaricus placomyces     Peck

Here are the characters that distinguish this species from the others in its group. For its more general characters, see higher up on the page.
If there's just a few words or a microscopic feature here, a more thorough description can be found above.


  • Cap greyish or silvery white; covered with tiny dark grey or greyish brown fibrils, or scaly tufts of fibrils
  • Flesh sometimes turning yellowish or pinkish if crushed
  • Sometimes with brown droplets on the underside of the unbroken veil; these leave brown stains on the veil when it breaks to form the annulus
  • Sometimes smelling phenolic

Microscropic Characters


In practice (at least from the descriptions I've seen), this mushroom is indistinguishable from its "look-alikes" Agaricus meleagris (=Agaricus praeclaresquamosus) and Agaricus pocillator. I have called the group Agaricus placomyces here because Agaricus meleagris is supposed to be a western species and Agaricus pocillator a southern one. So if you use one of those other names, someone may ask you what the difference is between your find and Agaricus placomyces, and you will have difficulty answering, because there probably isn't any.
Agaricus placomyces is supposed to differ from all other Xanthodermati by those brown droplets on the veil, even though they're not always present
Agaricus meleagris is supposed to be a larger and more robust mushroom (the upper limit on it's size given as 6" by Lincoff (1987) and 10" by Arora (1986) ) with a much stronger odor
Agaricus pocillator is supposed to have a two-layered partial veil cap fibrils more limited to the disk, and a bulbous stalk base. N. S. Weber & A. H. Smith (1985) also list its spore size as 5.5-6 x 3.8-4.5 Ám, with cheilocystidia 18-37 x 4.5-9 Ám
However, A. E. Bessette, D. W. Fischer & A. R. Bessette (1997) point out that they've found collections in which these characters were mixed and matched, so it's not clear how well these separations hold up in practice