Please do not re-click a link while waiting for a page to load. (It’s slower and degrades site speed for all users.)
To get images for machine learning, see MO Images for Machine Learning

Observation 2330: Hysterangium Vittad.

Ok, these are the weird find of the week. I was kicking up small dirt humps among this one live oak roots, where I have found R. cyanoxantha buried (And where I did find one R. cyanoxantha near by). But in one of the dirt humps, this small white ball popped up. I cleaned up the hump, and found a bunch of these whitish balls. They each have this one small “root”, and are kinda like a small two lobed potato. They have a hard thick whitish skin, with an interior spore mass. This points to the genus of Hymenogaster, with the small size and growth on live oak roots, this points to H. parksii, which was found in the notes for H. sublilacinus in Arora. The ball seems to have this strange band across them, which I tried to show in the third photo. The spore mass looks like a lot of squished gills radiating out from a central point on one end of the tuber, which I tried to show in the forth photo.

3/1/2008 – Update on this id, now using the Field guide to N.A. truffles. This is a small field guide of hypogeous fungi, most of them not truffles at all. It lists 90 species with photos, but a little frustrating to use. But with the photos here these are clearly not Hymenogaster. The off-white thick skim, and the radially wrinkled interior gets you to the genus Hysterangium. The guide mentions a couple species of this genus, but they seem to be under pines, and most important they have a mild odor. These were found under live oak, and were intensely odored, very funky and stong. That seems to be a better match for Trappea darkeri.

Both of these genus seems to be hypogeous forms of stinkhorns.

Species Lists


Proposed Names

-2% (3)
Used references: Field guide to N.A. truffles, p. 96.
66% (6)
Recognized by sight
44% (2)
Used references: p. 53 in Field Guide to North American Truffles. Key feature: thick peridium that stains pinkish to brown, with thick dendroid columella. (Yeah, that centralized rootlike rhizomorphs produces that interior gelatinous/rubbery vestigial stem called a columella, which in this species has become the interior widely branching structure. This could still be a species novum, too, because H. crassirhachis is not known from live oak, but could be associated with a Douglas fir that was 150 feet distant! These critters will fruit as far away from the trunk as the tree is tall. They also produce rhizomorphic matt communities, which tend to stabilize soils, especially on steep terrain.

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

= Observer’s choice
= Current consensus


Add Comment
Hysterangium for sure but what species
By: Michael Castellano (trufflercaz)
2009-07-07 18:13:42 SAST (+0200)

I concur that this is a Hysterangium species and probably would guess it to be Hysterangium separabile Zeller (sensu castellano). This is the oak associate that occurs from oregon to Mexico and has a polished smooth perdium and kinda husky spores for a Hysterangium species. I have recently proposed 3 new Hysterangium species from Mexico that associate with Oak and this might be one of those. I would have to study it to be sure.

Ok Hysterangium it is…
By: Douglas Smith (douglas)
2008-03-02 21:28:40 SAST (+0200)

Ok, this info makes the Field guide to Truffles even more frustrating. The only species of Hysterangium they mention are only found under pines or larch. No suggestion of Oaks there. Also they mention that the Hysterangium species are mild odored, to slightly fruity. Not like this one, which was pungent.

I wasn’t saving samples at the time, so I don’t have these anymore. But if Hysterangium is common under oaks in this area, I’ll take it.

Hysterangium or Trappea?
By: Michael Wood (mykoweb)
2008-03-02 03:37:36 SAST (+0200)

Definitely not a Hymenogaster, which does not have an olivaceous gleba. These are either Hysterangium or Trappea. Hysterangiums are much more common, in fact a Hysterangium (we used to call it H. seperabile, but I think that was a misnomer) is one of the really common truffeloid fungi under our local live oaks. Mature Hysterangiums have a VERY pungent odor.
Bote Hysterangium and Trappea commonly have the olivaceous green gleba. Trappea was segregated from Hysterangium by Castellano based on peridial features and the smooth spores of Trappea versus roughened of Hysterangium. Without scoping the collection, I would lean towards Hysterangium, since T. darkeri is associated with conifers and Hysterangiums are very common in the Bay Area with live oak.
Castellano, M.A. (1990). The new genus Trappea (Basidiomycotina, Hysterangiaceae), a segregate from Hysterangium. Mycotaxon 38: 1-9.
Zeller, S.M. & Dodge, C.W. (1929). Hysterangium in North America. Ann. Missouri Bot. Gard. 16: 83-128.
And if you are intereted in the phylogenetics of the gomphoid/phalloid clase:
Hosaka, K. & others. (2006). Molecular phylogenetics of the gomphoid-phalloid fungi with an establishment of the new subclass Phallomycetidae and two new orders. Mycologia 98: 949-959.
That puts Hysterangium in the Hysterangiales and Trappea in the Phalalles.