Day 269: By and large, liverworts are far less common than mosses and lichens, and thallose liverworts (those having a "leafy" structure) even less common. In fact, most of our local species closely resemble mosses, so separating them visually without a hand lens can be daunting. On the other hand, the thallose species sometimes look like lichens, and that factor was what drew my attention to this specimen. From a distance, I took it to be Peltigera venosa, but on closer inspection, the pores and gemma cups characteristic of Marchantia became obvious. Although difficult to see in this photo, just above center in the middle of the lobe and again in the center of the lobe to the left, these structures are evident, each cup containing several gemmae (the spore-bearing "eggs" of the species). "Liverwort!" I exulted to my botany partners, Joe and Sharon. "But that's as far as I'm willing to go."
At home, I turned to the only two field guides covering Pacific Northwest liverworts to any extent, certain that they'd be inadequate to the task. I got as far as genus: Marchantia. My specimen was considerably larger than Marchantia polymorpha (a common pest in greenhouses, and one of very few liverworts I can recognize in the field), so I referred it out to expert David Wagner, who identified it as Marchantia alpestris, a species which occurs at higher elevations.
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