Collection location: Rockcreek Park, Washington DC, USA [Click for map]
Habitat – growing on soil, near dead wood, gregarious, cluster of two specimens very close to each other and another approximately 50 cm away.
Pileus – white, dull, dry, with remnants of the universal veil (appressed scales), bruises initially light red and then becomes brown very slowly, round, convex to flat, flesh is white, margin is striated.
Hymenium – gilled, gills are white, crowded, free, smooth, margin is entire, crenate.
Stipe – white, hollow with cottony cluster inside, cartilaginous, tapered toward apex, with white volva at the base, flocose near apex, inserted, smell is weak and non-distinctive.
Pileus height – 22 mm
Pileus diameter – 48-50 mm
Stipe diameter at apex – 8 mm
Stipe diameter at middle – 9.5 mm
Stipe diameter at base – 13 mm
Stipe length – 120 mm
Volva height – 4.5 cm
[admin – Sat Aug 14 02:07:32 +0000 2010]: Changed location name from ‘Washington, DC, USA (Rockcreek Park)’ to ‘Rockcreek Park, Washington DC, USA’
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sum(score * weight) /
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1. Amanita whetstoneae doesn’t stain as strongly as the cap does in this pic.
2. Amanita whetstoneae doesn’t usually have the top of the sac turning in (in the picture it looks like an ovoid sac was stretched vertically; whetstoneae usually expands the cap while still within the saccate volva…often considerably widening the volva in the process.
3. The cap of Amanita whetstoneae tends to be a pale tannish color, perhaps with a slightly darker center; this mushroom is retaining white areas and staining a brick-red-brown around the wound.
To me, the above three items drop the probability of this being whetstoneae.
Of these two the more elongate volva is usually on dolichopus. The ratio of stem length to stem width (mid-stipe) in dolichopus is often greater than or equal to 10:1; in your case, the ratio is slightly more that 12:1 (120:9.5); the same ratio in pseudovolvata is frequently less than 10:1. So points are assigned to dolichopus from what we know at present.
What should you look for under the scope? Well the two critters currently under discussion are the two American species of sect. Amidella with the smallest average spore sizes. What I need to do is prepare something for you with the spore sizes and shapes. In addition, a cross-section of a gill is difficult to make because the tissue is so easy to crush; however, if you are willing to give it several tries with a very sharp razor blade…and if you are lucky in having gill tissue that cooperates (fresh or rehydrated), then these differences will be helpful to you.
1. Amanita pseudovolvata has thin gills. As in all amanitas there is central band running down the gill from the cap’s flesh to the gill’s edge. This band is called the “central stratum.” On each side of the central stratum the tissue (if you have a good section) should be seen to curve down and away from the central stratum on both sides. In both species the curving elements are often inflated cells of one shape or another (round, oval, club-shaped, etc.).
a. In pseudospreta the tissues involved in the curving include all the cells between the central stratum and the bottoms of the basidia on the two gill faces…with the possible exception of the last cell just before a basidium—-the cells from which the basidia arise may be perpendicular to the central stratum.The tissue of dolichopus is considerably different. In this species the curving bits produce numerous “parallel” rows of subglobose or globose or ovoid little cells; and these cell rows are perpendicular to the central stratum for their entire lengths. In other words, the curving bits turn into rows of cells with the centerlines perpendicular to the central stratum many cells away from the bases of the basidia.
I hope that that is clear.
If you’ve never made a cross section of a gill before, be patient. It is hard even for an experienced mycologist to get just the right thickness, etc. In fresh material the cells will move around more than in dried material; however, poorly dried material may refused to rehydrate…and then you just have to start over.
Some clues about doing microscopy on Amanita (including how to best rehydrate tissues is available under the heading “morphological methodology” (it’s a fairly big PDF) on the old Amanita Studies site.
Email me if you have more questions and/or want the spore measurement data of the two species mentioned above.
Stipe length is 12 cm. To me the volva was more on the elongated end than globose but I am not that experienced to say. The link you sent me has a mushroom incredibly similar to the one I found. I can have a look at mine at the microscope Monday but to be sincere I am not sure what I should look for ;-)
Do you have a stipe length (height)? I see the volva was 45 mm tall (about as tall as one of the cap’s was wide, with a volval sac that large (proportionately), I assume that is was much more tubular or elongated than oval or subglobose, is that correct? Since the top of the sac is not flaring, maybe A. whetstoneae (often larger than your material) is less likely.
Amidellas are very hard to determine from a picture or even with one in your hand. I rely on a microscope.
_ is a late June arrival in eastern PA and parts of NJ. But the elongate volval sack would be odd for that species. I’ll lean toward A. dolichopus, but would expect to have a good chance of being wrong.
Thanks for the comments. There were a lot of different mushrooms on Rock Creek Park today. I did not measure the largest of the three Amanitas on the cluster we found but I estimate it was around 12 cm wide. I updated the description of the one I posted so that you can see more details of it.
They look like they are all finding mushrooms, too! I am envious.
Can you tell me how big the largest mushroom was (height? cap width?). My impression is that it is very fresh. If that is the case, since there is not a large floccose mass around the top of the stipe, I think it is not likely that you have A. volvata. Can you tell me if the margin of the small mushroom in the picture had a notably striate cap margin? If the answer is yes, then that plus the lack of the floccose material around the top of the stem suggests either of two undescribed taxa instead of A. volvata: My suggestions are A. pseudovolvata Tulloss nom. prov. and A. dolichopus Tulloss nom. prov. The best way to separate these two is by the lamella trama. USUALLY (but not always) the stem of the second one is longer proportionately (about 10 times longer than it is wide). The cap is wider in relation to stem length in the first one.
If you want some information about the microscopy, you can email from mushroomobserver.org or from the Amanita Studies site.
Created: 2010-06-12 14:18:15 EDT (-0400)
Last modified: 2012-03-14 18:26:13 EDT (-0400)
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