Bryum dichotomum

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Identification notes

Bryologists have wrestled with what has become known as the Bryum dichotomum complex of bulbiliferous species for many years. Species have been described within that are no longer accepted (eg B.dunense), others are recognised on continental Europe but not in Britain and Ireland (eg B.barnesii), and new species have been described which are now accepted (eg B.dyffrynense). Bryum gemmiferum and Bryum gemmilucens are distinctly different and are generally accepted as good species. Within what we now call Bryum dichotomum there is a great variation in leaf characters but all have greenish bulbils in groups of up to 20 per axil (usually far fewer), with clear leaf primordia.

Bryum dichotomum is a very common species of disturbed ground that is tolerant of eutrophication and sometimes thrives on it. It is frequent beside paths, tracks, roads and in arable fields. When bulbils are present identification is usually straightforward, but it is not uncommon to come across plants with no bulbils which can be perplexing due to variability of this species. Some may be impossible to name with certainty.

Molecular taxonomy is likely to shed more light on this species complex with the strong possibility of cryptic species being present.

 

Read the Field Guide account

Distribution in Great Britain and Ireland

This is a mainly lowland species but in practice it is very widely distributed apart from in the Scottish Highlands.

View distribution from the BBS Atlas 2014

Resources you may find useful

Holyoak, D. 2021. European Bryaceae.

David Holyoak’s book contains keys, detailed morphological, ecological and taxonomic descriptions and diagrams showing key features – and is highly recommended for anyone wishing to get to know Bryum species.

The Bryophyte identification page under Resources contains additional information on the genus Bryum, including an early version of the keys now published in David Holyoak’s book.

Bryophyte identification resources
Holyoak, D.T. A taxonomic review of some British coastal species
of the Bryum bicolor complex, with a description of
Bryum dyffrynense sp. nov. Journal of Bryology, 25:2,
107-113

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