Identification notes
This is the commonest of the Calypogeia species, and whilst particularly a plant of damp acid or neutral banks and streamsides in woodland it will also grow on organic or peaty soils or Sphagnum in more open areas. It is usually fairly straightforward to recognise, but it can be quite variable, especially when growing in atypical and drier habitats. It can form quite extensive patches.
It is one of the more robust Calypogeias, with shoots usually 2mm wide or more. The leaf apex is narrowed, and many leaves will have a small notch at the apex. This is smaller than the widely spreading bifid apex of C.arguta. Not all leaves show this, so you may have to hunt along a stem to be sure. The underleaves are deeply bifid and sometimes have a blunt lobe as opposed to the sharper lobes of C.arguta. The other common species of this genus in similar habitats is C.muelleriana which has more rounded overlapping leaves and more shallowly notched underleaves. Gemmae on the branch tips are common. Most plants can be named with confidence in the field.
Oil bodies of fresh material are important confirmatory characters in this genus. In C.fissa they are multisegmented, rather like transparent blackberries, but other species can be similar. Details of the underleaves usually need microscopic study. The oil bodies in the rarer C.azurea are bluish.
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