Review of the identification and status of these small, delicate, often inconspicuous ferns.

There is a short key with line drawings of fronds, although spore characters necessitate use of a microscope in the second couplet. This is unfortunate since the species concerned (C. dickeiana) is protected under Schedule 8 of the 1981 Wildlife and Countryside Act. Perhaps the defence might be that it was reasonable to expect your finds to be another species, so long as you’re not collecting in locations known or likely to have C. dickeiana (sea caves near Aberdeen, rich montane arctic-alpine sites).