ESSEX   BOTANY   AND   MYCOLOGY  GROUPS 

This large subspecies of the common liverwort that inhabits garden paths and green houses is found in wet semi-natural habitats and differs from the common subsp. ruderalis and the northern subsp. montivagans in having an absence of air cavities below a continuous dark line along the mid-line of the upper surface of the thalli, and a tendency to  form rather larger, loose, flat or ascending as opposed to closely appressed thalli. In all three, on the underside there are six rows (3 each side of the mid-line) of long (several millimetres), very thin narrowly semi-lunate scales that have a rounded lobule at the widest point near the distal end. The margins of the scales have long unicellular papillae in all three subspecies, but the lobule has an entire margin in subsp. polymorpha and a dentate one in the other two. We only have four records of subsp. polymorpha for Essex.