The Essex Naturalist 133
Most lvs with both sides curved, apex often denticulate, often curving
downwards when moist, not transversely undulate;
Only slightly shrunken when dry, 1.2-2.4 mm long, asymmetric, decurrent
bases, with rounded cells, forming distinct auricles. Mid-1 f cells 10-16um
x 90-14um. Axillary fusiform gemmae often present. Sporophytes common
in S.E.England. Glossy, pale to dark green, on soil, decaying wood and
litter. Apparently calcifuge, but absent from strongly acid soils.
................................................. Plagiothecium denticulatum
var. denticulatum
Most Ivs with one +. straight side, apex usually entire, very flattened, lvs
transversely undulate, so closely appressed as to be difficult to separate
when wet;
Close to P. denticulatum, and possibly just a marshy ground ecotype. On
decaying vegetation and plant bases in Sphagnum bogs, marshes, carr and
reed swamps. Very local in the S.E. but sporophytes frequent where it
occurs......................................... Plagiothecium ruthei
Lvs tapering to narrow, acuminate, entire apex, cells 10-22um x 100-200um,
not in transverse rows, overlapping;
Fusiform axillary gemmae occasional. Dull or glossy, golden or dark green,
shrinking slightly when dry. Soil banks, tree bases, stream banks in woods,
hedgerows. Sporophytes occasional in the S.E. Absent from acid soils.
................................................ Plagiothecium succulentum
Lvs shortly tapered to entire or denticulate, acute apex, cells 16-22um
x 80-120um in H- transverse rows, scarcely overlapping;
Fusiform axillary gemmae occasional. Dull or glossy, golden or dark green,
shrinking markedly when dry. On soil in woods, hedgebanks, tree bases,
streambanks. Sporophytes occasional in the S.E. Absent from acid soils.
................................................ Plagiothecium nemorale
(P. sylvaticum).
Leaves NOT decurrent:
Lvs scarcely complanate. tapering to long fine apex, margin denticulate from
near base to apex, nerve short, double;
Mid-lf cells 5-9um x 60-100um. Pale yellowish-green, glossy. Rotting
stumps and logs, especially of Sweet Chestnut. Probably an introduced
species. Rare and sporadic, largely confined to S.E.England.
................................................. Herzogiella seligeri
(Isopterygium seligeri)
Lvs complanate. tapering to filiform apex, denticulate towards apex only.
Cells linear, 5-7um x 75-110um in mid-lf;
Axillary twiglike propagules with reduced leaves usually present and at
certain times of the year abundant in fluffy yellowish clusters easily seen
with a hand-lens. Glossy, pale green, on sloping banks and tree bases, on
neutral to acid soils in woodland. Calcifuge. A characteristic moss of the
London Clay and Claygate Beds......... Isopterygium elegans
'Twiglet-Moss'
Lvs complanate, hardly altered when dry, ovate, narrowed to short acute
apex, margin +. denticulate throughout:
Mid-lf cells linear, 6-10um x 50-80um. Pale green, flat patches on soil, tree
roots and bases, on flint stones. Calcicole. Very local in shady woods on
chalk or chalky boulder clay.............. Taxiphyllum wissgrillii
(Isopterygium depressum)