The Moss Families of the British Isles


L. Watson and M. J. Dallwitz



Excluding Anomodontaceae (Anomodon).

Gametophyte. Pleurocarpous; forming patches, or forming wefts (the branches often arcuate or homomallous). Shoots complanate, or not complanate (Abietinella). Paraphyllia present. The leaves of main stems and branches markedly different in form; ovate to narrowly lanceolate (sometimes deltoid), or lingulate; spiral. Leaf bases decurrent (Heterocladium), or not decurrent. The leaves double-nerved (Heterocladium), or single-nerved (Thuidium). The leaf nerves extending beyond the middle of the leaf, but not to the tip. Leaf blade apices obtuse, or pointed; apiculate, or not apiculate; apically acute, or acuminate. Leaf blade margins entire, or denticulate to dentate (or crenulate). Leaf blades not conspicuously bordered. The basal leaf cells somewhat longitudinally elongated to longitudinally much elongated; papillose. The angular cells not well differentiated. The mid-leaf cells somewhat longitudinally elongated, or longitudinally much elongated (Heterocladium, Helodium); hexagonal, or rounded, or rhomboidal; papillose. The walls of the mid-leaf cells thin to thick; straight, or sinuous.

Plants monoecious, or dioecious (mostly).

Sporophyte. Capsules exserted; inclined; curved; with an annulus. Calyptra symmetrical; splitting down one side. Capsules with a peristome. The peristome double. The peristome teeth not grouped; not deeply cleft; not perforated; thin, membranous, and transversely barred; exteriorly with a fine longitudinal dividing line between the transverse bars. The inner peristome well developed; shorter than the outer; with a basal membranous ring; with elongated “processes”; ciliate. The operculum conical, or mamillate, or rostrate. Setae long; reddish.

Ecology. Occurring in basic habitats, neutral pH conditions, and acid conditions. In diverse habitats.

Cytology. Haploid chromosome number, n = 10, 11, and 12.

British representation. 9 species. Abietinella, Heterocladium (cf. Pterigynandraceae), Thuidium. Northern Scotland, southern Scotland, northern England, English Midlands, East Anglia, Wales, southeast England, central southern England, southwest England, Isle of Wight, and Ireland.

Classification. Class Bryopsida; Subclass Bryideae; Order Hypnales (see classificatory comment under Pterigynandraceae).

Comments. The ‘fronds’ of Thuidium tamariscinum, comprising regularly, usually thrice-pinnately branched secondary stems, render this common species one of the most easily identified British mosses.

Illustrations. • Heterocladium: Dixon. • Abietinella and Thuidium, with Helodium: Dixon. • Thuidium, with Anomodon and Helodium: Berkeley.

To view the illustrations with detailed captions, go to the interactive key. This also offers full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2005 onwards. The moss families of the British Isles. Version: 21st June 2009.’.