Inocybe -- probably Inocybe geohylla (see Arora pg 460)

Posted by Elmer 12/16/12 - - - - -Scroll Down to See the Discussion

Note: Inocybe geohylla is poisonous- it contains "muscarine"


Small white - growing on wood chips


Gills are notched


Cap is dry and smooth


Shows color of stipe at top


Spore print is Orange Brown


Spores are eliptical
7 to 8 microns by
4 to 5 microns


Elmer:This is a little white mushroom growing on wood chips.
Cap is definitely umbonate.
The spore print is light brown or orange brown
the gills are notched.
The stipe was rather stiff. Am I correct that this is an Inocybe
as to sp. I get nowhere fast.
Sava: I would also say it's an Inocybe.
Have you checked the smell of it; many Inocybe have a distinctive spermatic odor.
Now that you're into microscopy, this mushroom is a good opportunity to look for cystidia.

What do we do with its "growing on woodchips" and the fact that Inocybe are mycorrhyzal?

Final question: How do we know, based on the info you've provided, that your mushroom is not a Hebeloma?

Elmer: 1) As to growing on wood chips -- the wood chips were under a conifer -
It certainly could have been Mycorrhyzal.

2) How do I know it is not Hebeloma:
the cap was not viscid and it was not Brown.
I do note that the key says that the stem of Hebeloma is "scurfy" at the top.
You may note that one of my pictures specifically shows the top of the stipe of my specimen.
It is somewhat "scurfy", but looking at Hebelomas, I think that they are more scurfy.

Sava Yes, the cap surface is different in the two genera.
Hebeloma has gelatinized cap cuticle
(though I'm not sure I can always recognize this character, or the absence of it, without the scope).
Inocybe has radially arranged hyphae in the cutticle,
a feature that often results in radially splitting caps,
which does show (a bit, but enough) in your photo.

However, the microscopic evidence is the most convincing:
the spores in your photo are definitely smooth,
whereas in Hebeloma they are warty.
This being said, the spores in your next Inocybe may surprise you---
they can also be nodulose (which is quite distinct from both "smooth" and "warty").

Click on a thumbnail below to enlarge the image