The revision by Murray (1988) recognised two
subspp. within A. rothii. Older records
of subspp. and vars. under the same names were based on partly
different criteria and may not be entirely equivalent. Murray
(op. cit.: 54) admitted
that there is a 'small amount of material with features in all
ways intermediate', but this appears to underestimate the
frequency of intermediate specimens. Indeed, Paton (1969a:
709) did not record these forms separately because they appear
to intergrade, and my own experience is that intermediate
so common in Cornwall as to render distinction between
them troublesome and apparently of little value. Many plants
seem to have leaf characters of subsp. falcata but only low
papillae on the inner perichaetial bracts. Intermediates are
also frequent in Devon (M. Pool, pers. comm.) and elsewhere in
Britain (T. L. Blockeel in litt.). Only
occasional attempts have been made to record the subspp.
separately during the present study, resulting in a paucity of
mapped records at subspp. level.
The species as a whole grows on unshaded granitic
rocks, on horizontal, sloping and vertical surfaces, including
boulders in old walls.
Commonly c.fr.: capsules immature 4, 9-11, dehisced