Well, I was reading my notes on this collection again, and something just didn’t sit right, so I consulted Agaricales of CA and looked at the color plate for A. diminutivus, as well photos here and on Mykoweb – they all looked somehow coherently different.
However, the color plate in Agaricales of CA for A. micromegathus looked much closer, so I did a line-by line comparison of the descriptions.
Aside from habitat, there were only 2 microscopic differences that varied enough to be useful:
1) The presence of orange-staining velar inclusions (in KOH) for A. diminutivus
2) a difference in size and aspect ratio of the basidia: smaller and with a low Q value ( less than 2, and more like 1.6 for A. diminutivus), larger, and with a higher Q (greater than 3) for A. micromegathus.
I examined tissues from my dessicated specimens, and I found no trace of orange inclusions in the velar tissue, and the Q avg for the basidia was 3.3. (L avg. 21.3 microns, W avg 6.4 microns).
Given this, I reexamined the habitat for the collection, and decided that it could be interpreted as “grassy” (scattered large clumps), and definitely “open”, and exposed trailside with little vegetation other than the grass and old oak stumps.
Anyways, I’m not completely convinced, but feel stronger about this ID – discuss away!
