Observation 174953: Retiboletus griseus var. fuscus
When: 2014-08-17
No herbarium specimen

Notes: I first posted these exactly 3 years ago — see http://mushroomobserver.org/74396?q=99DD.

They look pretty much like the regular oak-loving R. griseus. The only difference is that they grow under pines, have their stipes stain red instead of yellow and have much longer spores (11-17 × 4-6 μm vs. 9-13 × 3-5 μm in B-R-B).

[17/1/1] mounted in KOH; L x W = (11.2-) 11.6-16.5 (-17.2) x 3.7-4.7 μm;
L’ x W’ = 13.5 × 4.1 μm;
Q = (2.70-) 2.80-3.89 (-4.11); Q’ = 3.31

Proposed Names

92% (2)
Eye3 Eyes3
Used references: North American Boletes by Bessette-Roody-Bessette
Based on microscopic features: Spores larger than R. griseus and in agreement with the range reported in the above reference — see Notes

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Eye3 = Observer’s choice
Eyes3 = Current consensus


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That’s exactly…
By: Dave W (Dave W)
2014-08-23 16:16:33 CDT (-0500)

what I’m wondering.

By: I. G. Safonov (IGSafonov)
2014-08-23 16:14:46 CDT (-0500)

Besette et al. write on page 117 of their opus:
Boletus griseus var. fuscus, Hongo, formerly known only from Japan, has recently been collected on Cape Cod by Bill Neill…”. Mind you, “recently” is at least 15 years ago when the book was first published. :)
I wonder in anyone compared the DNA of the material from Japan and the USA to draw a definitive conclusion.

Spore size and Q…
By: Dave W (Dave W)
2014-08-23 11:58:02 CDT (-0500)

make the regular griseus seem highly unlikely.

The same as the Japanese var. fuscus…?

Created: 2014-08-23 00:23:03 CDT (-0500)
Last modified: 2014-08-23 11:53:47 CDT (-0500)
Viewed: 41 times, last viewed: 2017-06-18 16:43:54 CDT (-0500)
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