Identification notes
Like other Cephaloziella species, this one is very small. It is also very rare and is known only from a few places on the southern coast of England.
Unlike its relatives, C. baumgartneri is a calcicole and is known only from chalk, soft limestone or other base-rich sedimentary rock. That helps considerably with its identification, ruling out nearly all other similar species. It creeps about in quite dense dark green patches on shaded rocks or soil and its bilobed leaves are often widely spaced apart, a distinctive feature. It is also often fertile, and perianths can be abundant. An important identification feature that can just about be seen with a good x 20 hand-lens, but is far easier with a microscope, is a lobed sheathing structure formed from fused bracts and bracteoles around the bottom of the perianth.
In at least one of its sites, on the Isle of Wight, it lives on calcareous sandstone boulders brought downslope by undercliff slumps and it is able to colonise new sites as they become available. It tolerates shade generated by colonisation of stabilised slippages by scrub to some extent but may be eventually smothered by ivy.
