Blueing Bracket Postia subcaesia?

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Lee Dingain
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Blueing Bracket Postia subcaesia?

Post by Lee Dingain » Sun Jan 07, 2018 3:36 pm

Found a few of these small brackets yesterday on delaying logs of an old plane tree. I'm fairly confident they Blueing Bracket Postia subcaesia. The features add up, but apparently there is a similar species Postia alni that I can't find much information on, but apparently it it not as hairy on the upper surface? I'd be interested in anyone's thoughts.

1.9 cm wide, 1 mm thick, narrowly attached the wood.
Upper surface: blueish and faintly zoned (the first photo was taken in the field in very dull overcast conditions, the second photo was taken today at home in bright sun), completely covered in fine hairs.
Underside: white to grey, rounded pores, roughly 4 pores per mm.
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mollisia
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Re: Blueing Bracket Postia subcaesia?

Post by mollisia » Fri Jan 12, 2018 2:02 pm

Hello,

your polypore is not Postia subcaesia, but Trametes versicolor (Turkey-tail). Postia is much thicker, softer and not like leather, and moreover is not multizonate.

To diffenciate between Oligoporus/Postia subcaesia and alni is quite difficulte. O. alni should be tomentose on the cap surface instead of glabrous (as you already mentioned), the pores are slightly smaller (what I somewhat doubt ...) and the spores are slightly narrower (what I doubt even more): 1-1,3 vs. 1-1,5 is not really a big difference .... :roll:

best regards,
Andreas

Lee Dingain
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Posts: 45
Joined: Sat Dec 16, 2017 8:33 pm

Re: Blueing Bracket Postia subcaesia?

Post by Lee Dingain » Fri Jan 12, 2018 2:28 pm

Hi Andreas,

Many thanks for that. I have read in a few sources that P. subcaesia can actually be faintly zoned on the upper surface? I didn't realise Turkeytail can be blueish in colour like this? The First Nature website implies the blueish colour is diagnostic of he Postia group (although they only talk about Postia caesia?

I've been told that P. alni has 5-5 pore per 1mm whereas P. subcaesia has 4 - although I can't find any sources to verify this?

Best wishes,
Lee

mollisia
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Re: Blueing Bracket Postia subcaesia?

Post by mollisia » Fri Jan 12, 2018 2:42 pm

Hello Lee,

when you only take the genus Postia into account, than the blue colours are diagnostic for the group caesia-subcaesia-alni.

But blueish colours may occure in several polypores, e.g. in Ischnoderma also etc.
Blue zones are highly characteristic for turkey-tail, though it also may have zones in other colours. But WHEN the zones are blue, than - within Trametes - it can only be T. versicolor.
So the problem in your case is to see wether this is a Trametes or a Postia. And the thin, leathery fuitbodies show that it is Trametes and not Postia.

The zones of Postia caesia are not that sharpely delimitated one to each other, but the caps are only vaguely zoned.

The differences between Postia alni and P. subcaesia mentioned above are described e.g. in "Poroid fungi of Europe" by Leif Ryvarden. But they are more or less the same in "Polyporaceae" by Annarosa Bernicchia (Fungi Europaei vol. 12).

best regards,
Andreas

Lee Dingain
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Posts: 45
Joined: Sat Dec 16, 2017 8:33 pm

Re: Blueing Bracket Postia subcaesia?

Post by Lee Dingain » Fri Jan 12, 2018 2:56 pm

Hi Andreas,

Many thanks indeed for this, I really appreciate your detailed replies. Thanks also for the reference. I find the polypores really interesting but they are much harder to identify than I imagined. I'm about to post some photos of another I haven't got very far with!

Best wishes,
Lee

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