One Log, Two Arcyria Species

Day 235: After mistakenly identifying a specimen in the field (obvious to me once I got the photo up on the screen), I decided I was going to have to put a sample under the microscope. I made a second trip up to the site to collect some of the material, and lifted a small bit of what I assumed to be older: darker, expended sporocarps presenting capillitial filaments. Using a darkfield microscope at 1000x, I was able to observe the "cogs and half-rings" typical of Arcyria denudata and thought I had it nailed. However, upon seeing my photo of the lighter coloured sporocarps, a slime mold expert asked if I had considered A. obvelata. I defended my identification by citing the visible cogs I had observed on the capillitial filaments under the 'scope. That night, I did not sleep well, plagued by a nagging feeling that maybe there had been more than one species of Arcyria on that log, and what I had thought was older by virtue of its colour might in fact not be the same as the tan specimen. The following morning, I downed a second cup of coffee and headed out the door to collect another sample. What I saw under the 'scope confirmed that the lighter of the two was indeed A. obvelata. Its capillitial threads resembled rock candy, and the spores were 1-2 microns larger than those I'd observed from the first specimen. As a botanist, I should have known better than to take a sample from one specimen and a photograph of another, even one which was in very close proximity! As I studied the sample of A. obvelata under 1000x magnification, I was delighted to find a section which hadn't shed quite all of its spores on my kitchen table. In the top right photo, the circle on the left shows spores still attached to the capillitial strands.