Observation 83027: Postia guttulata (Sacc.) Jülich

Displayed at three California mycological events to upwards of a dozen pairs of taxonomicly-minded eyeballs, including six PhD professors (active and emeritus) with no positive identification yet.

Habitat: mixed redwood and tanoak forest

Substrate: unknown (collector unknown), though almost certainly saprotrophic. given material observed at base, either growing terrestrially in woody debris or directly on wood.

Taste: astringent, tart, pores seemingly milder.

Odor: conky, like sweet rubber bands


  • Shape: bracket- or fan-like, singular or comprised of multiple shelves up to 16cm in diameter, depressed at stipe apex (if present) or point of attachment, broadly to acutely fluted, radially undulating, occasionally splitting and recombining to form rounded holes or gaps, radially streaked (more apparent at margin). Margin straight.
  • Color: Off-white to pale yellow, some areas discoloring yellow/brown with age or bruising, dingier toward the disc which is dirtied by collecting fallen debris. Adorned with small (up to 1mm), circular to radially-elongated, semi-translucent dimples on all portions of the cap surface (though more concentrated toward the margin), resembling indentations left from exudative droplets.
  • Texture: Generally glabrous though unevenly and coarsely roughened by small granular pieces of included debris, which are more concentrated toward the disc.
  • Context: Rubbery but fragile, fibrous, breaking cleanly. Varying in thickness (~3mm-7mm). White and unchanging.

Stipe: Absent or, if present, then rudimentary, comprised of a short (~4cm), tough, fibrous, laterally-attached, bone-like portion of sterile tissue which gradually fans out into the pileus. Flesh distinctly firmer than throughout the rest of the fruiting body.

Hymenophore: Minutely poroid (5-6 per mm), annual, comprising a single layer of tubes of up to 5mm in length. Pores circular to rounded, frequently vertically elongated, mouths white though some areas latently discoloring dingy yellow or greyish-brown with age/bruising. Remaining tube length noticeably darker (pale grayish-green), dissepiments thin and finely lacerate.

Hyphal System: Dimitic skeletal. Both generative and skeletal hyphae thick-walled, skeletals considerably wider (up to 12μm), unbranching, with abundant single, double or multiple1 clamps at base, generative hyphae more slender (2-5μm) and slightly contorted, occasionally branching, with single clamps.

Spores: 1-guttulate, smooth, inamyloid2, oblong- to broadly-ellipsoid to subglobose, inequilateral in side view.

3-5×2-3μm (x=4.0×2.4μm, m=20, s=1)


1 I thought I had good pictures of this, but realized that my images don’t clearly show multiple clamps. will attempt to rephotograph soon.

2 Amyloidity difficult to determine. if present, then weak.

Species Lists


new camera in the mail. had to make do with crappy p&s for this.
400x KOH – pores
1000x KOH – hymenophoral trama & hymenium
1000x KOH – hymenium (basidioles)
1000x KOH – spore (crummy, I know. these were miserably hard to photograph)
400x KOH – hyphae
1000x KOH – clamp connection on thin-walled hyphae
1000x KOH – clamp connection on thick-walled hyphae
1000x KOH – clamp connection on thick-walled hyphae
400x Melzer’s – skeletal hypha

Proposed Names

-85% (1)
Recognized by sight: Black staining polypore
-29% (1)
Recognized by sight: pending microscopy
Used references: darv
58% (1)
Recognized by sight: inamyloidity removes Amylosporus as a possibility; the only genus proposed not in Polyporales.
29% (1)
Recognized by sight
69% (3)
Recognized by sight: the new name for O. guttulatus, according to IF.

Please login to propose your own names and vote on existing names.

Eye3 = Observer’s choice
Eyes3 = Current consensus


Add Comment
By: Danny Newman (myxomop)
2011-12-05 20:00:38 CST (-0500)

Desjardin confirms inamyloidity. Naturally, that takes this out of Amylosporus.

**edit: I commented on other A. campbellii observations of Darv’s on the complete absence of any mention of pinkish tones to the cap and pore surface in Gilbertson & Ryvarden’s description, despite its appearance in photo after photo of that species. This paper:

Dai, Yu-Cheng, Amylosporus campbelli, a noteworthy polypore new
to Southeast Asia.
Czech Mycol. 59(2): 171–175, 2007 (web.natur.cuni.cz/cvsm/CM59204F.pdf)

does note that characteristic. The description page for A. campbellii now includes Dai’s description.

By: Danny Newman (myxomop)
2011-11-28 23:18:46 CST (-0500)

As per its description in North American Polypores:

-subtropical distribution, reported from “the southernmost parts of California, Arizona and Texas.”

-spores “with minute scattered amyloid granules” (no mention of single, large guttule)

-“hymenial region blueish in Melzer’s reagent.” (not so here)

-dries light and fragile (these have a dried consistency of stale ginger snaps)

there are many characteristics in common, most notably the presence of double/multiple clamps; a trait apparently restricted to a select few polypores. So far, I’ve been unable to find a synoptic key/list of the taxa which possess them.

**note: the Osteina obducta proposal was destroyed on the basis of its pileus context being described as up to 3cm thick. the context here was scarcely 7mm.

By: Darvin DeShazer (darv)
2011-11-24 02:10:50 CST (-0500)

If it has amyloid spores, check out Amylosporus campbellii.

Created: 2011-11-22 16:56:10 CST (-0500)
Last modified: 2017-11-01 04:41:33 CDT (-0400)
Viewed: 349 times, last viewed: 2018-07-13 15:06:30 CDT (-0400)
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