Observation 181007: Caloboletus radicans (Pers.) Vizzini
When: 2014-09-25
Who: zaca
No herbarium specimen

Notes: Growing under Quercus trees. Very big specimen (cap diameter about 17 cm.

Proposed Names

55% (1)
Recognized by sight
Based on microscopic features: Spores with a lower Q ratio (due to being wider) are a better match for C. radicans than B. fechtneri:
C. radicans Spores 10–15 × 4–6 μm, ratio 2–3.1
B. fechtneri 9–15 × 3.5–5.5

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Eye3 = Observer’s choice
Eyes3 = Current consensus


Add Comment
You’re welcome!
By: Christian (Christian Schwarz)
2014-10-03 04:52:03 CST (+0800)

Nice to be put through the paces with all the appropriate data.

By: zaca
2014-10-03 04:43:56 CST (+0800)

Thanks again, Christian, for your help.

Q value is a ratio
By: Christian (Christian Schwarz)
2014-10-03 04:39:59 CST (+0800)

So you can look at the two numbers used in producing it – the length and width.
Yours are too wide for the range noted for B. fechtneri.

However; …
By: zaca
2014-10-03 04:36:09 CST (+0800)

according to www.boletales.com the value of Q of both species is very similar:
range 2–3.1 for B. radicans,
range 2–3.4 for B. fechtneri,
and thus cannot serve to decide between the two species in this case.

By: Christian (Christian Schwarz)
2014-10-03 04:28:48 CST (+0800)

Quick work, as far as I can tell, this points to C. radicans (wider spores, often higher Q ratio)

Microscopy added.
By: zaca
2014-10-03 04:23:59 CST (+0800)
Thanks, Debbie, for the link…
By: zaca
2014-10-03 03:42:52 CST (+0800)

but that is my usual reference for Boletales.

Butry. fechtneri can indeed show a gray cap …
By: Debbie Viess (amanitarita)
2014-10-03 03:31:01 CST (+0800)

but the stipe here looks wrong for that species.

Here is a page on Boletus (now Butyriboletus) fechneri. It shows spores, to which you can compare yours.


By: Christian (Christian Schwarz)
2014-10-03 03:29:09 CST (+0800)

Cyanoboletus is not a new name for C. radicans, which is a bitter bolete.

The reddish stipe occurs fairly often in C. radicans (and the closely related “marshii”), although you may not find that in any “official descriptions”.

Cyanoboletus does not have the true, extensive reticulum or the large, stout stature pictured here.

Unfortunately …
By: zaca
2014-10-03 02:37:20 CST (+0800)

I didn’t taste it. However, I have a small sample and I will look for the spores, at least.
Thanks, Christian, for your reply.

The stipe and cap look very gray
By: Christian (Christian Schwarz)
2014-10-03 02:16:36 CST (+0800)

The flesh looks rather pale as well. It may be Butyriboletus fechtneri, but I believe that cap often will show a little more reddish-brown in it.
More importantly, the pores and flesh of Butyriboletus should be yellower.

The best way to tell, of course, would be to taste it!
Butters will be mild, while the taste will be bitter in Caloboletus.

Thanks, Christian, for your proposal.
By: zaca
2014-10-03 02:05:42 CST (+0800)

Can you ellucidate about the differences between the two species?

Created: 2014-10-01 06:17:31 CST (+0800)
Last modified: 2014-10-03 07:56:44 CST (+0800)
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