A crippling view of a 'ringtail' hen harrier below the overlook was one of the high points of the day. The other was finding Andreaea rupestris on a number of sandstone slabs in the sheep-grazed moorland.
The leaves of Andreaea rupestris are somewhat falcate-secund with a sheathing base.
Unlike A. rothii, the leaves of A.rupestris don't have a costa and unlike A. mutabilis the basal marginal cells are rectangular.
Basal cells of leaf
The prominent papillae on the abaxial side of the leaf are a feature of A. rupestris.
Confusion with A. mutabilis (absent from South Wales) is possible, but the leaves of that species lack a sheathing base, have a distinct patch of yellow cells near the base and have basal, marginal cells that are more or less circular (isodiametric). Andreaea alpina is usually a much bigger plant, with leaves that are a different shape, with sinuose basal cells, denticulate basal margins and lack prominent papillae on the abaxial side.
A. rupestris is much less common than A. rothii in South Wales. For example, there were only 3 previous records in the Mapamate database for VC41, all from the vicinity of Craig y Llyn and only one of those (courtesy of SDSB, BS and GMT from their Craig y Llyn trip last autumn) is recent. However there's a lot more habitat like this to explore in upland Glamorgan, particularly in RCT and Bridgend, so I think we'll be able to put a few more dots on the map in the near future. Among the other mostly unremarkable species we recorded were Racomitrium fasciculare (which is abundant here) and Ptychomitrium polyphyllum - typical species of exposed, acid rock on our moorlands.