Observation 81616: Peziza vesiculosa Pers.

When: 2011-10-29

Collection location: Tillamook Co., Oregon, USA [Click for map]

Who: Danny Newman (myxomop)

Specimen available

Even more interesting than seeing this was hearing Sava’s repeat attempts to pronounce “Don’s donkey dung.”

Growing on… donkey dung.

Species Lists


400x Melzer’s – spores & ascus tips
1000x Melzer’s – spores & ascus tips

Proposed Names

29% (1)
Recognized by sight: Coprophillic, apothecia up to 2cm (considerably smaller than P. vesiculosa also found on dung).
Used references: Larsen, H.J. Key to the genera of the operculate cup-fungi (PEZIZALES) of the Pacific Northwest and Rocky Mountain Region. Pacific Northwest Key Council. Nov. 7, 1980. (http://www.svims.ca/council/Peziza.htm)
Based on microscopic features: Intense bluing at ascus tips, spores ~18×10μ
40% (3)
Recognized by sight

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= Observer’s choice
= Current consensus


Add Comment
I agree with Sava
By: Irene Andersson (irenea)
2011-11-08 16:29:57 CST (+0800)

In my keys P. fimeti is even smaller (up to 10 mm), outside glabrous, and more brown rather than tan.
P. vesiculosa 20-100 mm – and of course even smaller when they’re young.

I agree
By: Danny Newman (myxomop)
2011-11-08 16:19:57 CST (+0800)

that not only the substrate but the season (P. fimeti is said to grow in the spring) is a little off, at least according to the PNWKC Pezizaceae key. But in order for this to be P. vesiculosa, even the largest fruit bodies we saw would be too small to occupy even the tiniest end of P. vesiculosa’s the apothecium diameter range, if they even fit at all. According to the PNWKC key, they don’t.

P. fimeti is up to 2cm.
P. vesiculosa is 5-8cm.

The quarter is 2.5cm wide. If the largest of the cups was to go completely planar, it still wouldn’t measure 5cm.

Also, my 5-6 hurried spore measurements came out to roughly 17-19×9-11, which fits the range for both P. fimeti and P. vesiculosa… but if this is P. fimeti, we have to contend with several ranges in spore size, as mentioned toward the end of this MushRumors article:


Taking all of those authors’ measurements into account, the range in spore length becomes 13-20μm. P. fimeti’s substrate, according to the same article, is herbivore dung, plain and simple, meaning more mammals than one.

So… where from here… I wonder…

Don’s donkey dung fungus
By: Ruzica and Sava Krstic (ruzasava)
2011-11-08 14:35:21 CST (+0800)

The spores measured 20-22 × 11-13 microns. That’s a little too large for P. fimeti, but falls into the range for P. vesiculosa.

P. fimeti is said to grow on cow dung and P. vesiculosa on horse dung (closer to donkey).