
Bifid Crestwort
A leafy liverwort - these plants go waaaaaay back. Liverworts are considered to be amongst the first true plants and have been around for something like 400,000,000 years! They rather like the wet, so are quite common around here, often mixed in with mosses.
http://www.naturespot.org.uk/species/bifid-crestwort

This liverwort is a translucent, pale green in colour with shoots 2 to 4 mm wide sometimes stretching to sevral cm in length. The conspicuously bilobed leaves are 2 mm in length with the lobes drawn out to a long, narrow point. The underleaves are also bilobed, with an additional lateral tooth on each side. The plant is strongly aromatic, and often fertile, with toothed perianths.