*1: (Paton 1984: 5, Corley 1985:
21).
*2: Caradon Hill, 1962,
JAP (Paton 1984: 5, Corley 1985: 21).
See notes under preceding species. C. nicholsonii has most
of its localities in Britain and Ireland, with a record from
Germany. Most of the British sites are in
Cornwall.
Distinction between this species and C. massalongi relies
mainly on its larger size, most easily assessed from the stem
cortical cells, and the larger and often irregularly shaped
gemmae (Paton 1999: 152). However, shaded material is often
unidentifiable or only rather tentatively identifiable from
the large size and frequent irregularity of the
gemmae.
Forming mats, mainly pure, often locally dominant.
On thin soil and deeper soil or clay in areas of old
copper-mine spoil, usually where evidently very copper rich
and most plentiful in damp places. Also on walls built from or
retaining mine spoil, where it grows mainly on 'soil' in
crevices but sometimes spreads over rocks around crevices. On
vertical to horizontal substrates. Occurs in open unshaded
situations and where very sheltered and partly shaded. Large
patches occur on flat open ground near an exposed cliff top at
Botallack, but near Minions and elsewhere it grows luxuriantly
on sheltered and partly shaded banks of a small stream. It
apparently persists for many years when its sites become
heavily shaded by encroaching scrub or saplings, although
identification becomes difficult if not hopeless with plants
growing in shade.
Although differences in habitat preferences from C. massalongi have been
reported, none appear consistent so that list of associates
could mainly serve for both species. Those recorded include Cephaloziella
stellulifera, Dicranella varia, Pohlia annotina, Scopelophila
cataractae. Also overgrowing ground-litter of decaying
grasses or mosses on old copper mine spoil, on partly bare
stony ground at edge of path near old mines, on steep
sandy-silt alluvium of bank near Red River (presumably
containing copper). See below for analyses of its substrates
at Cornish sites.
Foliar gemmae usually (always?) present, often
abundant, especially in shaded plants which often have few
leaves, none of them properly formed, but masses of gemmae.
Perianths only occasionally present: very immature 2, 12, well
grown 1, 4. Capsules not seen.
Chemical analyses of its substrates
show it can tolerate high to very high levels of Cu at Cornish
localities, whereas levels of Pb and Zn are not exceptionally
high at these sites. All substrates investigated were
acidic.
Analyses of substrates from
localities in
Cornwall
(metal
concentrations given as µg/g dry
weight):
LOCALITY (N samples) Cu
Pb
Zn
pH
Source
Long Lane, vc1 (2)
161-464
42-139
7-10
6.0
Clements (1996)
Tuckingmill, vc1 (1)
179
3
20
6.0
Clements (1996)
Dolcoath
Road, vc1
(6)
1678-3450
56-90
240-723
5.2-6.8
Rouen
(2000)
Gilbert's Coombe, vc1 (4) 2024-3512
82-288
245-485
5.1-5.4
Rouen
(2000)
W. Bassett, vc1 (4)
1316-3039
35-65
31-78
5.1-5.9
Rouen
(2000)
