A variable taxon; includes plants with brownish
tubers; others with tubers small (120-180 µm diameter, cfr, in
DTH). Several
populations in Isles of Scilly have tubers of typical shape
and size, but yellow, brownish-yellow or yellow varying to
orange (DTH).
Dutch workers have advocated merging this species with B. rubens, but it is
usually distinct in the narrower leaf cells and lack of a
well-defined leaf border of ca 3 rows of very
narrow incrassate cells. Holyoak & Pedersen (2007) present
DNA sequence data showing they are only distantly related
species.
Habitat notes from Cornwall are as follows. On
patches of mainly bare soil on unshaded tops and slopes of
serpentinite and slaty sea-cliffs (with Acaulon muticum, Ceratodon purpureus).
Colonising thin soil over serpentinite rock in old quarry
above sea-cliff, unshaded (with Trichostomum
brachydontium, Tortula truncata).
Abundant on unshaded soil over shaly rock on and above
sea-cliffs. Unshaded soil on 'hedges' above sea-cliff.
Unshaded humic soil on coastal heaths. Plentiful as colonist
on partly bare, acid, dumped soil (flat areas and banks) near
china clay quarries (with Bryum dichotomum, Ceratodon
purpureus,
Trichodon cylindricus, Tortula truncata).
Recently burnt humic soil on slope above creek, part shaded by
open Sessile Oakwood (with Ceratodon purpureus).
Partly bare acidic soil on tracks, including those on old
mining ground, on heathland and in a conifer plantation, also
on a grave, unshaded to part shaded (with Ceratodon purpureus).
Earthy mine-spoil on unshaded slope (with Bryum rubens, Dicranella
staphylina, Phascum
cuspidatum var.
papillosum,
Trichodon cylindricus, Tortula truncata).
Peaty soil of open area on heathland. Sandy soil in short
grassland at edge of brackish pool, unshaded. Unshaded
sediment exposed high in inundation zone beside Stithians
Reservoir, with sparse low vegetation (including Leptobryum pyriforme).
Twice in arable fields, including cereal stubble (with Bryum dichotomum, Bryum rubens, Dicranella
staphylina,
Trichodon cylindricus, Tortula truncata).
Other associates recorded include Bryum argenteum, Bryum
dichotomum.
Frequently (commonly ?) c.fr.: capsules immature 1,
3-5, 7, 10, 12; dehiscing 7.