*1: Near Camborne,
1861, WC (PNZ) (Paton 1969a: 727). This
record is older than that published as new for vc1 by Warburg
(1962: 370).
*2: Carbis, NW. of
Bugle, 1963, JAP (BBSUK) (Paton 1969a: 727).
[Earlier report (St Minver, in Tellam 1892) not supported by
specimen: Paton 1969a: 727].
Smith (1978: 277) gives a short seta [ca 1.5 mm] as a
character by which var. densifolia differs
from the common form, but such short setae have not been found
in abundant Cornish material, which has setae 3-5
mm.
Differs from var. controversa in forming
denser deeper tufts with stems 15-45 mm high and in having
leaves of almost uniform size evenly spaced along the stems.
However, the gametophyte characters of some Cornish
populations of var. densifolia grade into
more typical plants of var. controversa. One of
several similar examples is that at West Chyverton mine there
were tall tufts of var. densifolia on an old
wall, apparently typical var. controversa on
mine-spoil 'lithosols' nearby, along with various
intermediates. Young populations of var. densifolia probably
look much like var. controversa until the
characteristically taller stems develop, so it may be that the
tallest tufts develop only in the most stable sites such as on
walls, or on the sites with highest metal levels. However,
well-grown patches c.fr. at Roseland (SE. of Liskeard)
restricted to band beneath a galvanised iron shed roof were
all of perfectly ordinary var. controversa,
demonstrating that not all ecotypes tolerant of heavy metals
are of the var. densifolia
phenotype.
Forms deep cushions, tufts or more extensive
patches and most often occurring in substantial quantities,
judging from which it may clearly become a long-established
perennial. Habitat notes from C&S are as follows. Grows on
soil, old concrete, old mortar or in crevices of stone walls,
in free-draining places that are fully insolated or only
partly shaded. It often grows on substrates that are evidently
calcareous and also often on those that must have high levels
of copper or zinc, or which receive run-off contaminated by
these metals. Most records are from old mortared-stone walls
(of barn and other buildings, walls beside tracks and a
stream); also recorded four times from slopes of copper mine
spoil. Several records are associated with zinc run-off from
galvanised iron: on horizontal old concrete, stone walls and
soil at bases of galvanised sheds (sometimes covering several
square metres), beneath galvanised railings and a galvanised
gate, below an old fence made of galvanised wire and on
concrete at base of leg of electricity pylon. Zinc run-off
might also account for records from near to stored pipes and
machine parts on a low bank of china clay spoil, but it is
less evident with several records on china-clay spoil at base
of large concrete clay-settling tanks (where it grew along
with shorter plants that match var. controversa).
Plentiful on damp timber (which was originally tanalised, i.e.
treated with fungicides?) beneath galvanised-wire netting on
boardwalks on damp ground near Argal and College Reservoirs,
in light to moderate shade. Several other finds were also not
associated with any obvious metalliferous contamination: on
thin soil over rocks of open hill top (Carn Brea near Land's
End); extensive mainly pure patches on unshaded gravel area
close to edge of estuary (Sunny Corner). Commonly forms pure
patches. Associates recorded were Bryum pallescens
(frequent records) and (once each) Pohlia flexuosa and Pohlia
nutans.
Commonly cfr, but also occurs as large non-fertile
patches at some localities; capsules immature 1-3, 5 (6
few), 10-12; dehiscing 3, 5; dehisced
4-7.
