Although the seller describes it as a liverwort (it does resemble a leafy liverwort in the auction photograph; perhaps this is why he chose to describe it as such), Plagionium is actually a moss genus. I'm unable to find any information on any aquatic Plagionium species, though I can't say for sure that none exist. However, if he is just selling a terrestrial moss grown immersed, that might explain the moss' appearance as well as the slow growth rate mentioned in the auction.
The US Department of Agriculture has a page with information on a few US-native Plagionium species at http://plants.usda.gov/java/profile?symbol=PLAGI7, if you're interested.
Hope this helps!
-Chris
Bookmarks