The other day at the Dunwoody Nature Center, I came across a peculiar plant hugging the surface of a rock. The first word that came to mind was moss, but I think now it is probably a liverwort.
Liverworts are close relatives to mosses; they used to be classified in the same division but are now separate. In the old days, people believed liverworts helped cure liver diseases and that is how they got their name. Mosses comprise the division Bryophyta while liverworts now make up the division Marchantiophyta. There are thought to be about 9,000 species of liverworts on earth, while there are closer to 16,000 species of mosses. Mosses differ from liverworts in many ways. Most mosses have a costa, or rib, on their leaves, but liverworts lack these. Most leaves on mosses do not have large lobes or segments to them but liverworts usually do. Also, if it is hard to distinguish the stem from the leaf, it is most likely a liverwort. Most liverworts are smaller than many mosses, only growing 2-20 mm wide and 10 mm long. Liverworts have single-celled rhizoids as opposed to the multi-celled rhizoids of mosses. Like mosses, however, liverworts reproduce through use of spores.
The liverworts one can most easily tell apart are thallose liverworts, which are flattened, horizontal, leathery, branching and green. Leafy or scale liverworts contain the most species with flat stems and overlapping leaves that form ranks.