For recognition of subsp. papillosum see Blockeel (1995). P.
cuspidatum s. l.
consists of var. cuspidatum and var.
papillosum, but excludes var.
The characters of var. papillosum (spinulose
spores, small upper lamina cells, strongly papillose upper
lamina cells) all occur independently. Hence many specimens
are intermediate between var. acaulon and var. papillosa (e.g. from
SE. of Cape Cornwall, by Basset's Cove, St Austell, near
Rosteague), with e.g., variably spinulose spores but only
weakly papillose upper laminal cells; spinulose spores but no
papillae on cells of upper leaf laminae and upper laminal
cells rather large (ca
20 µm wide);
blunt projections on spores but leaf characters of var. papillosa. Several
specimens have also been seen with ornamentation on the spores
consisting of a mixture of spinules and shorter blunt
projections. Both vars. have sometimes been found close
together, e.g. in stubble fields at St Erth and near
Rosteague, on soil heaps SE. of Tolver, on soil in grounds of
St Austell College, or close to intermediate plants. Overall,
the frequency of intermediate plants suggests there is little
point in recognising var. papillosum, which is apparently much
commoner inCornwall than elsewhere in Britain.
Notes on habitats in C&S are as follows. A
colonist of bare mineral soil, of mildly acid to basic
reaction, often where sandy but also where silty, loamy or
much compacted, but usually where free-draining. Commonest in
unshaded places or lightly shaded (e.g. by grasses and herbs),
but sometimes partly shaded by trees. Typically on partly bare
soil in many situations including beside paths and tracks, on
banks, soil patches in grassland, on roadsides, in arable
fields (stubble, grass leys), in gardens, cemeteries and
churchyards, on soil heaps, in plant-pots. Also recorded on
and above sea-cliffs, in quarries, at edge of gravel car park,
soil amongst old mine-spoil, on dredgings from ditches and on
silty mud exposed at
reservoir edge. Frequent associates include Barbula convoluta, B. unguiculata, Bryum argenteum, B. dichotomum, B. rubens, Dicranella
Tprtula truncata; others recorded are Bryum
Ephemerum minutissimum, Microbryum
M. rectum, Tortula modica, Anthoceros
Fossombronia pusilla, F. wondraczekii, Riccia glauca, R.
An unusual form collected at Cadgwith (from soil
patches in short grassland of a cliff-top car park) has large
numbers of leafy non-fertile stems (DTH
Commonly c.fr. (only recorded as this form when
spores mature): capsules immature 1-3, 6, 7, 11, 12; dehiscing
1, 3, 8-12.