My bad. I have just consulted with “Diversity, Ecology, and Conservation of Truffle Fungi in Forests of the Pacific Northwest” by James M. Trappe, Randy Molina, Daniel L. uoma, Efren Cazares, David Pilz, Jane E. Smith, Michael A. Castellano, Steven L. Miller, and Matthew J. Trappe (General Technical Report PNW-GTR-772, April 2009), which states that C. caespitosa has been found in the Pacific Northwest and in Europe. They state there are four species from north temperate forests, and question whether the three species known from Oregon and California actually belong in Chamonixia. That said, the photo describing C. caespitosa by Michael Castellano shows a strong central columella extending completely through the gleba, enlarging at the base to form a vestigial stipe (kind of like many Macowanites) that stains dark blue. That portion of the columella within the gleba also stains blue. I believe Caz said the material stains blue very quickly, and that mere rolling of the specimen can make the entire peridium look like a blueberry.

which fits with this specimen. those dark brown spores in the micrograph were unstained, and they colored the spore mass.
I’m gonna stick with this ID until proven otherwise.

Off to Oregon (the land of dial-up), so no more comments from me possible for another week or so.

Should still see at least a portion of columella, although in a different planar arrangement. The columella is like the woody parts of a deciduous tree: cut thru parallel to the ground, there should still be strong limbs and trunk present. Chamonixia caespitosa should be nearly black in the interior when mature: very similar to and hard to distinquish between Hymenogaster parksii, with the exception of the blue staining, usually in the peridium. Another Chamonixia species is still possible: one with dark brown gleba.

and the columella was cut in half rather than lengthwise? there are traces of something in the gleba that could account for that.

the locules were much more obvious and deeper on site with a handlens, less obvious perhaps as the gleba browned.

the spores are a very good match, with the size within range, a brown color and longitudinal raised ribs; even the little plug at the end.

There are two distinquishing factors for Chamonixia, neither of which are present in these photos that I can see. 1) Locules absent. I see none at highest possible magnification, where there should be hundreds. 2) Lacks columella. Looks more likely to be a Tuber species, but not any species I am aware of. Might even be something new to science.

spores were shot at max power (1000x oil immersion), but you can enlarge them even more by clicking on the photo on the MO site.

I did a bit of a search and came up with species match. Thanks for the genus lead, guys.

This is a secotioid fungus related to leccinum!

Both important extensions to known areas.

The specimen with rhizomorphs may not be a Tuber. Tubers rarely (never in my experience) form rhizomorphs. But the peridium certainly looks Tuber like with venae externae. Possible Chamonixia? I can’t say, as I have never found or seen that species. Would need to see spores from that specimen.

The second, dark brown collection may be Fischerula, which has a unique spore enveloped in cottony brown spine extensions, making it look like it is wrapped in cotton. This will only be apparent at extremely high power, so need to blow the spores up even further than you currently have.

spores were neither spiny nor warty but had weird broadly bumpy coats…no photo yet; I looked at them in NC.

That’s very interesting. Is it possible that this truffle (or even the whole genus Octaviania) is actually a clade of hypogeous, gasteroid Lactarius descendants?

A white peridium that blues quickly might be Octaviania, which often has a scanty latex when cut. How about some microphotos of the spores to see if they have BIG spines or warts.

… but first we’ll need pictures. :)