Favoritos de outside_observer

Fruiting beneath Sitka Spruce and Western Hemlock.
Completely viscid/glutinous(cap to stem base).
Mucous taste: Very bitter!
Odor: steamed Broccoli. Strong.
Cap margin with vibrant white band.
Harvested 5 specimens for further study/microscopy.
Spore Print: rusty brown/orange.
Spores: ellipsoid, verrucose/roughened, thick walled. Medium sized.
Dehydrated all specimens and bagged for herbarium collection/genetic record.
My coinciding Mushroomobserver observation below-

https://mushroomobserver.org/507746?q=1nsRj

Substrate: Tsuga canadensis snag
I most often find this species on birch, and every description I have found specifies hardwood only as substrate.
I believe P. squarrosoides has a history of being routinely misidentified as P. squarrosa, and the conventional wisdom is that they are practically indistinguishable macroscopically. However, I have concluded, along with many others, that they can be distinguished from one another based on the shape of their cap scales. My understanding is that the cap scales of P. squarrosa tend to be exclusively flattened/recurved throughout development. Those of P. squarrosoides are roughly conical, or claw-shaped, or irregularly clumpy when the mushrooms are young, and persistently so in the central area of the cap; as the cap expands, the scales closer to the margin tend to get stretched flat. With drying, the scales shrink and darken. I have also noticed from studying observations that P. squarrosa appears to fruit most commonly at the bases of trees or from the ground, presumably from buried wood, while P. squarrosoides most often fruits directly from wood.
I believe the abundance of images of P. squarrosoides that are misidentified as P. squarrosa gives the false impression of a complete overlap of macroscopic characteristics. I am skeptical of the current descriptions of these species, because when misidentification is so frequent, it's hard to know whether the descriptions were crafted around the actual species or misidentified specimens. For example, I have recently encountered a couple reports of alliaceous (onion/garlic) odor associated with observations that are clearly P. squarrosoides in my view. The conventional wisdom is that an alliaceous odor is proof of P. squarrosa; I now doubt this. Likewise, conifer wood is mentioned as possible substrate for P. squarrosa, but not P. squarrosoides. That doesn't convince me that my find here is P. squarrosa; I believe the descriptions are simply incomplete.
I find P. squarrosoides frequently in my local forests but have never found P. squarrosa. What I know of P. squarrosa comes from studying the observations of others. Observations from my region seem to reveal a pattern of abundant P. squarrosoides, and rare but not absent P. squarrosa.

Interesting find, I had never seen a white pluteus until today. Fruiting off old conifer logs, distinctive pink tinged gills. They smelled slightly cucumbery from a distance.

Cap: White, umbonate, texture smooth, pileipellis looks slightly fibrous. Center of the cap has darkened, brown fibres, radiating outwards. Cap 8.3cm in diameter.
Taste: Pleasant, a little nutty, turning sour, slightly acidic.
Gills: Closely spaced, salmon pink, younger specimens’ [gills] were white. Free, completely detached from stipe.
Stipe: White, bare. Fibrous, snaps similarly to celery.
Annulus: Not present.
Volva: Not present.
Spore print: Dull salmon-orange
Spore morphology: Thick walled, slightly angular.
Cheilocystidia: Present and abundant.
Pleurocystidia: Present, with apical prongs.
Caulocystidia: While observing shavings of the stem, I saw some meduloid-like structures. Not sure if they could have just been hyphae (Check image 12)

Images 1-5: Specimens in situ.
Images 6,7: Spore print.
Image 8: Spores, 2000x.
Image 9: Meduloid cheilocystidia on gill edge, 2000x.
Image 10: Drawing.
Image 11: Pleurocystidia and cheilocystidia together, 2000x.
Image 12: Possible caulocystidium on stipe, not quite sure, 500x.
Image 13: Cells on pileipellis, 500x.
Image 14: Pleurocystidia with apical prongs, 2000x.
Image 15: Cap from above.

P. petasatus arrived at via dichotomous key, generously provided by Michael Kuo on mushroomexpert:

https://www.mushroomexpert.com/pluteus.html

Observation #255