*1: Madron Moor, 1867,
WC (PNZ) (Paton 1969a:
711).
*2: Glynn valley, E. of
Bodmin, before 1907, RVT (B) (Paton 1969a:
711).
On the basis of isozyme evidence, var. perigoniale was
reported to be indistinguishable genetically from P. commune var. commune (Derda &
Wyatt 1990, Wyatt & Derda 1997: 288), leading to
speculation that characters used to distinguish varieties in
P. commune are merely
phenotypic responses. Similarly, var. humile seemed likely
to have little or no genetic basis. However, DNA sequence data
(Bijlsma et al.
2000, Van der Velde & Bijlsma 2000, N. Bell unpublished)
and culture experiments (Schriebl 1991) have led to a
reappraisal and two European species are recognised by Hyvonen
& Bell in Hill et
al. (2006:
203). The latter authors use the name P. uliginosum (Wallr.)
Schriebl for the familiar tall plant of bogs and marshes,
reserving P. commune s. str. (includuing var.
perigoniale) for a
shorter plant occurring in drier habitats, up to 5 cm tall,
with the end cells of the costal lamellae flat or weakly and
unevenly grooved. Hill et al. (2008) do not
adopt these names 'pending a more thorough revision of the
taxonomy of Polytrichum' and their
treatment as var. commune and var. perigoniale
is followed here, although var. humile is retained for
reasons discussed below.
A few recent records do not name the variety. These
are mapped as var. commune since it is by
far the commonest taxon and the small rarer forms would be
likely to attract attention.
Habitat notes from Cornwall for var. commune are as follows.
Characteristically forming patches or tall turfs on wet,
acidic substrates in mires, flushes or on wet heaths, often
with sphagna. Commonly in open, but also partly to rather
heavily shaded by GreyWillow
carrs, young birch woodland or edges of
conifer plantations (probably persisting from former more open
conditions). Occasionally in flushes on slopes above
sea-cliffs. Recorded associates include Sphagnum
denticulatum,
Sphagnum fallax,
Sphagnum fimbriatum, Sphagnum palustre, Sphagnum papillosum,
Sphagnum
squarrosum,
Sphagnum subnitens; sometimes amongst Juncus acutiflorus, J. effusus or Molinia caerulea.
Others recorded include Carex rostrata, Erica tetralix, Hedera and Ulex gallii. Once seen
adjoining Polytrichastrum
formosum at edge of wet hollow.
Also recorded in various drier habitats where often
less tall, non-fertile, and not infrequently distinguishable from
Polytrichastrum
formosum only by checking microscopic characters. Examples
include on steep, unshaded slopes among rocks near tors, on
rather dry grassy slope in old granite quarry, on banks and
stream- and river-sides in open areas in deciduous woodland
and under Grey Willows, flushed laneside bank, and on rather
dry soil near rocks in deciduous woodland. Often found as a
colonist on disturbed, wet or damp, acidic ground, such as
path and track edges and around old quarries. Records of such
colonists include bits on clay banks etc. in and near working
china clay quarries and on spoil heaps, larger patches on
flushed ground below old china-clay spoil heaps and on floor
of old pit, bits at edges of mica dams, and hollows in old
metalliferous mining ground, especially in wet hollows or
where flushed. Atypical records are of it being locally
plentiful on sediments (sandy, gravelly and humic) of open,
wave-washed edge of a reservoir, in places submerged by
shallow water for parts of each year (a few records also from
inundation-zone edges of other reservoirs); on peaty soil of
plant-pots in several places at Burncoose
Nursery.
Frequently c.fr.: capsules immature 3-7; dehisced
8-10.
