*1: Castle Horneck near
Penzance, 1866, WC
(PNZ) (Paton 1969a: 751).
*2: Trehane near
Probus, 1857, JS (TRU) (Paton 1969a:
751).
A variable species, with some plants apparently
intermediate in gametophyte characters between this and
preceding species. An unusual form with strongly plicate
leaves found occasionally, e.g. from beside R. Tamar near
Gunnislake.
Habitat notes from C&S are as follows. It grows
mainly in wetter sites than those preferred by B. rutabulum, but their
ranges overlap in moist sites and they often occur together.
Often plentiful on wet ground in flushed areas, streamsides
and near rivers in deciduous woodlands and on wet ground in
Grey Willow carrs, where lightly to rather heavily shaded,
growing on soil, damp rock, decaying wood, leaves and ground
litter. Associates include Calliergonella
cuspidata,
Conocephalum conicum, Oxyrrhynchium
hians, Kindbergia
praelonga, Hookeria
lucens, Lophocolea
bidentata,
Plagiomnium undulatum, Plagiothecium
denticulatum var.
denticulatum,
Rhizomnium punctatum, Chrysosplenium
oppositifolium,
Oenanthe crocata, occasionally Calliergon
cordifolium,
Chiloscyphus pallescens.
Other detailed habitat notes from Cornish sites are
as follows. Commonly on silty-loam of banks in flood-zone of
R. Tamar. Damp ground near reservoir edges, with Calliergonella
cuspidata. On clay soil in short grassland on bank (sea
wall) beside R. Tamar, unshaded. Damp grassland, including
pastures, damp slope in churchyard. Damp track in light shade
of Sycamores (with Calliergonella
cuspidata). Plentiful on wet disused railway track in
cutting. Mesotrophic to lightly acid areas of open mire.
Unshaded stream edges and flushes on and above sea-cliffs
(with Oxyrrhynchium
hians). On
top of rocks in quick-flowing stream in open near coast.
Colonist in damp to wet hollows in areas of china clay spoil,
sometimes near working quarries, unshaded or part shaded by
Grey Willows. Damp lawn. Damp grassland on slope in pasture.
Base of Juncus (J. acutiflorus, J. effusus, J. inflexus) and grasses
in wet rush-pasture (with Calliergon
cordifolium,
Calliergonella cuspidata), and in fen. Damp gravelly
ground at edge of road. Flushed patch on laneside
bank.
Often difficult to separate from B. rutabulum, which
fruits much more commonly, so fruiting records of B. rivulare need careful
checking. Frequently c.fr.: immature 1, 2, 10, 11; dehiscing
3, 11; dehisced 2-5.
