*1: Soil in shallow
dried-up pond on heath near Porthgwarra, St Levan, Land's End,
Sep. 1962, JAP (BBSUK)
(Warburg 1964: 728, Paton 1969a: 731).
*2: Roche, 1888, RVT
(BM) (Paton 1969a: 731). This is much earlier
than record published as new for vc2 by Warburg (1965b:
865).
Var. minutissimum of
Blockeel & Long (1998: 110) is treated as a separate
species here following Risse (1996, 1997) and Holyoak
(2010b).
While identification of the species is
straightforward, many old records of the varieties of E. serratum are in doubt
because their identification was often based on leaf
characters (as given by Dixon 1954: 293-294 and Smith 1978:
350), which appear to be unreliable (cf. Crundwell in Hill et al. 1994: 40,
Holyoak 2010b). The characters of ripe spores (more coarsely
papillose in E. serratum var. serratum, which also
lacks the persistent 'veil' commonly present in var. minutissimum) appear
to be consistent in allowing two taxa to be separated (Holyoak
2010b).
Virginia S. Bryan (1999 and in litt.) regarded
var. minutissimum
as based merely on var. serratum with immature spores, but
this seems to be untrue of British material, although immature
specimens of the latter might be confused with the former. No
intermediates have been seen inCornwall,
so that Risse (1996, see also his Errata 1997) is apparently
correct in regarding them as distinct species. Unlike the
commoner var. minutissimum, var. serratum has not been
found in arable fields in Cornwall. Both vars. have
been found growing close to each other on exposed sediments at
Stithians Reservoir, but they have not been recorded actually
growing together in Cornwall.
E.
serratum grows as scattered plants or forms sparse low
patches, the tiny gametophores growing from a thin layer of
persistent protonemata. Habitat notes from Cornwall are as
follows. The largest populations (with patches up to 50 cm or
more across) are recorded from firm surfaces of soil and
sediments exposed high in the inundation zones at edges of
several reservoirs and in an old flooded china-clay pit. At
these sites it occurs on silty, clayey, loamy or peaty
substrates that are mildly acidic to circumneutral and which
tend to remain damp but not wet, both in open places and
partly shaded by Grey Willows. These populations probably
reappear from persistent spore banks in each year when summer
water levels fall sufficiently low. Other records are of
scattered small patches on unshaded mainly bare soil of
disturbed ground beside paths just above sea-cliffs (of
serpentinite and slate), on a damp cattle-poached track,
beside paths and tracks at wood edges, on damp clay of path
among Calluna
vulgaris in old china-clay 'dry' and on wet soil of a
hummock in an unshaded acidic flush. Often in pure patches;
associated species recorded are Archidium
alternifolium, Bryum dichotomum, Dicranella rufescens,
Dicranella
staphylina, Trichodon cylindricus,
Entosthodon
obtusus, Kindbergia
praelonga, Fossombronia
wondraczekii, Gymnocolea inflata, Pohlia camptotrachela,
Pseudephemerum
nitidum, Riccia
glauca, Riccia
sorocarpa, Riccia
subbifurca, Tortula
truncata; single records also with Ephemerum sessile, Leptobryum
pyriforme.
Mature spores are needed for identification, but
capsules apparently develop on almost all female gametophores.
Capsules immature 7-12; dehiscing 7,
9-12.