When you encounter this plant, which typically grows gregariously on sandstone in sheltered places, you are most likely to think it is a species of Seligeria, for that is what it most resembles.
However, the substrate (if you know what it is) should set alarm bells ringing as Seligeria usually prefers limestone of various kinds. Do the plants have mature and dehisced capsules? When dry, they are distinctly furrowed if they are Brachydontium and smooth if they are Seligeria. Moist plants collected and taken home will quickly reveal their true identity once they have dried out.Read the Field Guide account