The Moss Families of the British Isles


L. Watson and M. J. Dallwitz



In Dixon’s Grimmiaceae.

Gametophyte. Pleurocarpous (with irregular branching); forming tufts, or forming patches (yellowish- or glaucous-green). Stems without a differentiated central strand. The leaves oblong to ovate, or ovate to lanceolate (concave); spiral; sometimes (falcato-) secund, or not secund; nerveless. Leaf blade apices pointed; apically acute to acuminate; conspicuously hyaline (H. ciliata), or not hyaline. Leaf blade margins at least proximally revolute or recurved. Leaf blades bordered to not conspicuously bordered. The basal leaf cells longitudinally much elongated; narrowly rectangular, or linear; papillose. The walls of basal leaf cells thick; sinuous. The angular cells clearly differentiated (the cells rectangular to transversely so). The mid-leaf cells somewhat longitudinally elongated; quadrate, or rectangular, or rhomboidal; papillose (the papillae simple or branched). The walls of the mid-leaf cells thick; sinuous.

Plants monoecious; autoecious.

Sporophyte. Capsules immersed to emergent, or exserted (but no more than shortly exserted); erect; symmetrical; if more or less elongated, straight; shortly sub-cylindric (obloid), or pyriform; with an externally conspicuous apophysis to without an externally conspicuous apophysis. Calyptra fugacious, small; symmetrical; not plicate; splitting down one side. Capsules without a peristome. The operculum conical. Setae very short; straight.

Ecology. Xerophytic; occurring in acid conditions. On dry, exposed, siliceous rocks, walls and roofing slates, at low to moderate altitudes.

Cytology. Haploid chromosome number, n = 10 (or 10 + 1), or 11, or 21, or 22.

British representation. 3 species. Hedwigia. 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 Hedwigiales.

Illustrations. • Hedwigia ciliata and Hedwigia integrifolia. Hedwigia ciliata. H. integrifolia. • Hedwigia, with Grimmiaceae and Ptychomitriaceae: 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.’.