Day 346: Marchantia polymorpha (a liverwort) is a common pest in nurseries and greenhouses, and that's how it came to find a home in my front flower bed. I "imported" its spores in a pot of Wintergreen, the thallus not yet developed and visible, and although I've tried to eliminate it by removing the infected soil, it continues to reproduce abundantly. You see, Marchantia is sex-crazed. It reproduces in any of three different ways: by spores contained within the gemmae found in the gemma cups (left), by spores contained in the receptacle (right), or via pieces broken off the main thallus (vegetative propagation). That's "sexessive" even among other thalloid liverworts!
This is the first time I've observed the receptacle (cute little palm tree!), and no wonder; they're supposed to appear in spring, to be followed in summer and autumn by the gemmae. When it releases its spores, they can be carried some distance by wind. On the other hand, the spores in the gemmae wash out onto the soil when the cups fill with rain, much like the peridioles of Bird's-Nest fungi. It's doubtful I can win out over such a complex and successful reproductive strategy, so I might as well just start thinking of my flower bed as a field laboratory for liverwort biology.
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