Observation 155854: Postia caesia group

Code: Bot_759/2013_DSC8535

Habitat: Mixed forest, Picea abies and Fagus sylvatica dominant, almost flat terrain, calcareous ground; full shade; humid place, partly protected from direct rain by tree canopies; average precipitations ~ 3.000 mm/year, average temperature 4-6 deg C, elevation 1.000 m (3.300 feet), alpine phytogeographical region.

Substratum: on dead rotting branch laying on ground and on half buried rotten roots of Fagus sylvatica, partly still in bark.

Place: Zadnja Trenta valley, left bank of (mostly) dry Soča river bed (Sušec), north of Bavški Grintavec Mountain, East Julian Alps, Posočje, Slovenia EC

Comments: This observation was first determined as Postia caesia (see former text in brackets below). But, kind explanation of Mr. Günter Sturm, Germany, having long ‘mileage’ in Polyporaceae, and the paper of David (1974), Ref.: (8) convinced me that the correct determination should be Postia subcaesia. Now substratum fits better. Also habitus of the find fits better to the new determination. Pileus of P. caesia is of more uniform colors and never has strongly contrasting colors as in this observation. Another trait, which fits better now, is the fact that the pilei color didn’t changed distinctly blue when bruised. Nevertheless, spore dimensions still don’t fit to data from literature. May be Ryvarden’s comment in Ref.: (7), p 405, regarding distinguishing both species: ‘However, there are some disturbing intermediate specimens on hardwoods.’ explains the situation?

((The text of former comments: This beautifully blue polypore may also be Postia subcaesia, syn.: Oligoporus subcaesius. Unfortunately, the distinguishing traits between P. caesia and P. subcaesia seem to be treated quite inconsistently in the literature. Postia caesia should principally thrive on wood of conifers (with rare but well documented exceptions) and should have spores wider than 1.5 μ, while Postia subcaesia is found on broadleaved trees and should have spores narrower than 1.5 μ (as per Refs.:(5), (6) and (1)). Contrary, Ref.: (4) states narrower than 1.5 μ spores for P.. caesi (mistake?). Also the information about spore shape (allantoid versus cylindrical) and pilei size is inconsistently given in different sources. In this observation measured spore width speaks in favor to P. caesia (according to Ref.:(1), (6) and (5)), while substratum doesn’t. Since exceptions with regard to substratum of P. caesia are known, and based on quite distinctively blue color of the pilei I decided for P. caesia, but this may be wrong.))

Growing in a small group of about 6 pilei of different size; pileus up to 6 × 4 cm across; flesh soft, fibrous; SP very faint, whitish(?), oac857(?).

Nikon D700/Nikkor Micro 105mm/f2.8

Species Lists


Strongly contrasting colors of the pilei.
Measured spores in comparison with data from literature for Postia subcaesia.

Proposed Names

28% (1)
Recognized by sight: Bluish sporocarp and soft texture.
Used references: (1) A. Bernicchia, Polyporaceaes.l., Fungi Europaei, Vol.10., Edizioni Candusso (2005), p 332.
(2) S. Buczacki, Collins Fungi Guide, Collins (2012), p 490.
(3) M. Bon, Parey’sBuch der Pilze, Kosmos (2005), p 316.
(4) R. Phillips, Mushrooms, Macmillan (2006), p 313.
(5) G.J. Krieglsteiner (Hrsg.), Die Grosspilze Baden-Württembergs, Band 1, Ulmer (2000), p 548.
(6) J. Breitenbach, F. Kraenzlin, Eds., Fungi of Switzerland, Vol.2. Verlag Mykologia (1984), pp 272-274.
Based on microscopic features: Spores smooth, cylindrical and moderately allantoid. Dimensions: 5.3 (SD = 0.2) x 1.6 (SD = 0.1) μ, Q = 3.25 (SD = 0.26), n = 30. Olympus CH20, NEA 100x/1.25, magnification 1.000 x, oil, in water.AmScope MA500 digital camera.
47% (2)
Recognized by sight: Id’ed by Mr. Günter Sturm, Germany
Used references: (1) Personal communication with Mr. Mr. Günter Sturm. Id’ed by Mr. Günter Sturm.
(2) J. Breitenbach, F. Kraenzlin, Eds., Fungi of Switzerland, Vol.2. Verlag Mykologia(1986), p274.
(3) A. Bernicchia, Polyporaceaes.l., Fungi Europaei Vol.10., Edizioni Candusso (2005), pp 359.
(4) S. Buczacki, Collins Fungi Guide, Collins (2012), p 490.
(5) R. Phillips, Mushrooms, Macmillan (2006), p 313.
(6) G.J. Krieglsteiner (Hrsg.), Die Grosspilze Baden-Württembergs, Band 1, Ulmer (2000), p 560.
(7) L. Ryvarden, R.L. Gilbertson, European Polypores, part 2., Synopsis Fungorum 7., Fungiflora A/S (1994), p 435.
(8) A. David, Une nouvelle espece de Polyporaceae: Tyromyces subcaesius, Bull. Soc.Linn. Lyon, Vol.46. (1974), pp 119-126.
56% (1)
Recognized by sight: There are 24 species in the P. caesia complex of which 12 are documented from Europe
Used references: Miettinen et al. 2018
28% (1)
Recognized by sight: brown cap in age, narrow spores, on Fagus and other deciduous trees

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Created: 2013-12-18 10:13:40 EST (-0500)
Last modified: 2018-04-21 12:16:16 EDT (-0400)
Viewed: 138 times, last viewed: 2018-12-02 00:07:07 EST (-0500)
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