*1: Near Camborne,
1861, WC (PNZ) (Paton 1969a:
748).
*2: Trescoll Moor near
Rocke, 1924, FR (BM) (Paton 1969a:
748).
D.
aduncus was split into three segregate species by
Zarnowiec (2001), but after detailed study of British
specimens Hill (2002, 2003) regarded these as merely
distinctive phenotypes of a 'remarkably plastic'
species.
Grows in various moist and wet habitats, or
shallowly or intermittently submerged, in basic to rather
acidic places, unshaded to lightly or partly shaded. More
detailed habitat notes from Cornwall are as follows. Damp and
partly bare areas on wet heathland and in marshy heaths, on
Lizard pen. and near lower Red
River. On old mine-spoil, in marshy areas with
sparse acidophilous vegetation, in shallow acidic pools, in
damp hollows that flood in winter, on damp paths or tracks and
their edges, on a bank and in moist gravelly areas, all sites
unshaded (with Amblystegium serpens
var. serpens, Calliergonella
cuspidata, Didymodon insulanus, Rhytidiadelphus
squarrosus). Soil at edge of small stream, slightly shaded
(near Sithney). On thin wet soil where water trickles around
ruin of concrete wall of china-clay works, lightly shaded. Wet
areas on concrete near china clay works. Calcareous
dune-slacks, on wet humic soil of edges of pools that flood in
winter, in short vegetation or extending into edges of taller
fen vegetation, unshaded or partly shaded by Grey Willows.
Plentiful on wet calcareous sand in flushed floor of disused
sandpit (with Aneura
pinguis, Bryum
pseudotriquetrum,
Brachythecium
rivulare, Calliergonella
cuspidata, Dicranella varia, Pellia endiviifolia,
Petalophyllum
ralfsii). At Hayle Kimbro Pool growing emergent or
submerged in shallow water, locally to 20 cm depth in summer;
growing intermixed with Myriophyllum
alterniflorum, Pilularia globulifera,
etc. High in inundation zone at edge of Stithians Reservoir,
on ground dry for part of each year, some parts shaded by Grey
Willows. Seasonally dry edge of Croft Pascoe Pool among
macrophytes and near to Sarmentypnum
exannulatum growing in oligotrophic water. Forming mats or
pure patches, or among other plants, on damp ground and in
pools in calcareous dune-slacks near north coast (locally
plentiful at Penhale Sands, recorded also at Gwithian Towans
and Upton Towans): growing among sparse low herbs at marshy
edge of slack, in small shallow pool near spring in flushed
area above low sea cliff, in unshaded edge of shallow
calcareous pool in dune-slack, and submerged in shallow
temporary pool in slack. St Agnes: unshaded damp ground beside
pool, at base of Potentilla anserina,
Holcus lanatus, Bolboschoenus
maritimus. Hayle Kimbro Pool: among open cover of herbs at
unshaded margin of large, partly dried pool (Drepanocladus
polygamus and Drepanocladus
sendtneri also known nearby). Treskillard: in short patchy
turf on unshaded ground of old mining area. Hayle Kimbro Pool:
in shallow edge of large pool, amongst macrophytes (mainly Littorella uniflora,
Hydrocotyle
vulgaris, Eleocharis
multicaulis, charophyte). Lower
Carnkie: on moist vertical concrete just above
water of small trough in disused mine buildings, slightly
shaded. Goss Moor: on unshaded muddy soil of partly bare patch
in damp acidic grassland. On damp flushed slope of china-clay
spoil above pit (with Calliergonella
cuspidata).
Not seen c.fr.
