Identification notes
Chionoloma is a confusing genus, the identity of its species further confused by previous identities (Trichostomum, Oxystegus). C. hibernicum is a hyperoceanic species that is best known to Scottish and Irish bryologists. In recent years its range has extended to include mountainous parts of Wales but it is either absent or very rare in England.
It is smaller than its common relative, C. tenuirostre (leaves commonly only a few mm long), and sometimes more brightly coloured. In some ways the plants resemble a Didymodon, although they grow in places (such as rocks near waterfalls or on montane crags) where any Didymodon is unlikely. If you section a stem of C. hibernicum, you should see an outer row of pale, thin-walled cells (the hyalodermis), something that is almost always absent in Didymodon. In the field, useful field pointers to Chionoloma include an expanded, sheathing leaf base, plane leaf margins and a nerve disappearing in or below the leaf tip. Unless you are very familiar with the species, microscopic checking is highly advisable.
Smith’s flora predates the current taxonomic concept of Chionoloma and it is advisable to refer to the resources listed below to find out more about all of the species and to identify them with keys.
Read the Field Guide account
