You’ll only find this scarce pleurocarp on limestone of some kind, its favourite being hard Carboniferous Limestone. Despite being sometimes abundant in a locality, it is not an especially distinctive moss and may easily be passed over as an Isothecium or even Cirriphyllum crassinervium.
It has broadly triangular stem leaves that can be seen to be slightly pleated with a hand-lens (examine dry plants – this feature is almost impossible to see when the leaves are wet). This can cause confusion with Eurhynchium striatum, a much more robust moss which does not normally grow directly on limestone.
Moss-covered, shaded drystone walls and limestone rocks in sheltered woodlands are favoured habitats of this species. When moist, colonies have a much-branched, spiky look as well as a certain green-gold hue not shared by Isothecium myosuroides. Capsules are more frequently produced in some districts than the books suggest.
Under the microscope, confirm the faint pleats of the stem leaf (far less obvious than Eurhynchium striatum), the cordate-triangular stem leaf shape and importantly, alar cells which form a group extending across the leaf base to the nerve.Read the Field Guide account