*1: Bellair, Mylor,
1838, EAW (TRU) (Paton 1969a:
740).
*2: Grogley Down, W. of
Bodmin, before 1907, RVT (B) (Paton 1969a:
740).
Usually forms small, pure cushions or patches.
Habitat notes from C&S are as follows. Mainly on hard dry
acidic rocks (usually granitic or slaty, once shale), growing
on open surfaces or in small crevices. Recorded most often
from man-made sites in old quarries, quarry spoil, boulders
among old mine-spoil, old walls (including bridge walls, a
reservoir dam and north wall of church), masonry debris,
graves, granite fence-posts, in 'hedges', and a road cutting.
The few natural sites recorded include low on sheltered
sea-cliff and a granite boulder in the flood-zone beside a
small river. It is often but not always found in sheltered
places, and tends to avoid exposed hill tops, but usually
grows unshaded or lightly shaded (occasionally part-shaded,
e.g. by woodland edge or buildings, rarely in heavy shade e.g.
in wooded old quarry). Although typical of acidic rocks, it
apparently tolerates some base. Patches found on rock in
mortared walls were all or mainly on acidic parts of the
substrates, but four scattered records of it (well-grown and
fertile at three of the sites) on old concrete suggest
tolerance of a basic substrate, especially as one of these was
close to Didymodon
rigidulus and Tortula
muralis.
Commonly c.fr. ; capsules immature 1-5, 10-12;
dehiscing 2-6 [7]; dehisced 4, 5, 7, 8,
10-12.
