I don't know what a "slime filament" looks like so I had to use a Key other than the Madrono Doyle and Stotler key. I really wish I had a better key for this area.
I used my British field guide to ID this as endiviifolia based on the teeth on the perianth mouth. The guide even had a drawing of teeth on a perianth mouth to make it simple.
When I colleced this I noticed that it seemed more frilly than P. neesiana and I thought it might be a different species or even genus.
The second picture shows elators and spores.
I think this is Marchantia polymorpha but the thallus is larger and the antheridiophores are smaller than the only other ones I have ever seen. Also I did not see any gemmea cups and I looked for them on several plants.
Ok now I think the other Marchantia that I found in town is subspecies ruderalis and this one here by the river is subspecies polymorpha.
The Marchantiophyta /mɑrˌkæntiˈɒfɨtə/ ( listen) are a division of bryophyte plants commonly referred to as hepatics or liverworts. Like other bryophytes, they have a gametophyte-dominant life cycle, in which cells of the plant carry only a single set of genetic information.
