Soil embankments, absurdly tiny. Doyle & Stotler write, "The study of these plants requires a steady hand, a compound microscope, and a high frustration threshold." Sigh. At least you can see that the leaf margins are dentate, which Doyle and Stotler seem to imply is unique to species without underleaves, though it's hard to tell what's top and bottom on this liverwort.

Mentioned this to Jim Shevock at CAS and he said these turn black when they're dry so they're essentially impossible to see on a backdrop of soil until it gets wet.