Wahlenbergiella striatula forme noire.

      His form is characterized by its dark colorations, grey-black, bronze-black, black-purple, etc., almost always with greenish reflections and frequently associated with, or alongside, Wahlenbergiella striatula forme verte. Level and very often with the red algae Hildenbrandia rubra.

    To be differentiated from certain forms coming low on the foreshore of Hydropunctaria amphibia with larger perithecia and a very black thallus without green reflections.