Identification notes
This hoary, cushion-forming moss of rock in hilly areas is normally easy to recognise (or suspect) as a Grimmia, although it is most often seen without any capsules. In fact it’s easier to identify when its dry than moist as shoots show one of its most important features: leaves spiral around the stem in a characteristic string-like fashion. This twisting is a result of a nerve that looks slightly S-shaped from above, although under the microscope this feature is not always that well developed. If you manage to find whippy shoots hidden within the cushions then check that they have concave leaflets with incurved leaf tips – this character sets the plants apart from most – but not all – of our other species of Grimmia.
Important microscopic characters are a stem which has a thin-walled central strand surrounded by thick-walled, orange outer cells (stem section needed to see this) and guide cells that lie obliquely (nerve section needed).
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