Observation 26313: Amanita abrupta Peck

When: 2009-09-21

Collection location: Big Thicket, Tyler Co., Texas, USA [Click for map]

Who: Ron Pastorino (Ronpast)

No specimen available

The photos are not the greatest for detail and this specimen may not be typical for the species, but it seemed to have most of the characteristics of A. abrupta.
The annulus became more prominent after a few hours. The spores were amyloid, roundish to broadly elliptical and about 7.7 X 6.5 microns.

[admin – Sat Aug 14 01:58:33 +0000 2010]: Changed location name from ‘Big Thicket, Tyler Co. Texas’ to ‘Big Thicket, Tyler Co., Texas, USA

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The spore picture now has red circles.
By: R. E. Tulloss (ret)
2009-10-06 22:27:20 CDT (-0400)

Ron was very kind to post my alteration of his picture of spores. For some reason after all the spore pictures that have been posted this year, I suddenly realized there is a way to use a spore picture without a scale…; and I haven’t mentioned it on MO so far as I can remember.

If you expand the spore picture, you will see three spores circled with red and labeled “A,” “B,” and “C.” I chose these spores because they are approximately in side (lateral) view, which is THE position for measuring Amanita spores if you want repeatable results. Really…why not?

There’s no scale in Ron’s picture so we can’t be exactly sure from the picure about spore sizes. However, we can be sure about shapes. And Bas gave us a way of converting the length of a spore divided by its width into nonnumerical (qualitative) spore shape terminology.

I used a mm ruler to measure the spores on my screen (the image was displayed at 100% size in Photoshop). Spore A was 17.2 × 14.0 mm (length is provided first). The Q value (spore length/width ratio) is 17.2/14.0 or 1.23 (broadly ellipsoid). Spore B is 15.0 × 14.0 mm, with Q = 1.07 (subglobose). Spore C is 16.7 × 12.5 mm, with Q = 1.34 (ellipsoid).

So now we have the macroscopic characters for A. abrupta (discussed below) and we have some numerical information about the shape of the spores (which are subglobose to ellipsoid). The range of Q for 3 spores (I measure at least 20 when I’m working up a specimens) is 1.07 – 1.34. That’s really not a bad estimate (in this case) because the range of Q I have recorded from 97 abrupta spores is “(1.07-) 1.10 – 1.40 (-1.61).” This set of numbers is read as follows: 1.07 is the smallest Q I ever saw in abrupta. 1.61 is the largest. 5% of the spores seen had Q less than or = to 1.10. 5% or less of the spores seen had Q > or = 1.40.

[If we were to translate my set of numbers to qualitative terms, we’d find that the shape of the spores in abrupta varies from subglobose to broadly ellipsoid to ellipsoid (and infrequently slightly elongate).]

The point I want to make is that you can get Q values from spores no matter what the scale of magnification happens to be…even though you may not be able to estimate the sizes of the spores. If you have data for spore Q values (they’re supplied for all species in the picturebook/checklists on the Amanita Studies website), then you can compare your Q values to the Q values that someone else has observed for the species in question.

Here’s Bas’ table for conversion from Q to qualitative terms:

1.0-1.05 globose
1.05-1.15 subglobose
1.15-1.30 broadly ellipsoid
1.30-1.60 ellipsoid
1.60-2.0 elongate
2.0-3.0 cylindric
greater than or equal to 3.0 bacilliform

Thanks Ron!


The bulb…
By: R. E. Tulloss (ret)
2009-10-06 20:54:36 CDT (-0400)

The bulb is typical of the species (the top bearing concentric rings of tissue) and so are the rather large pseudorrhizae attached near the bottom of the bulb. Even though the veil has not dropped it does appear to be attached to bundles of fibers that seem to be pulled from the stipe surface. This frequently happens in A. abrupta and in a few other taxa that don’t fit the general picture with this observation.


Created: 2009-10-06 17:22:22 CDT (-0400)
Last modified: 2011-03-17 11:21:07 CST (-0500)
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