The Moss Families of the British Isles


L. Watson and M. J. Dallwitz


Tree-fern Beauty-moss.

Gametophyte. Acrocarpous; plants small, pale green, slender, from a persistent protonema. Primary stems erect to procumbent. Mature plants with shoots to about 1 cm long. Shoots complanate. The leaves bilaterally symmetrical to markedly asymmetrical; elliptical to oblong (the laterals), or orbicular (more or less, the abaxial leaves, which are smaller); 3-ranked (the dimorphic leaves in three ranks, reminiscent of the vegetative organization of some liverworts); not crisped when dry; not plicate. Leaf bases not sheathing. The leaves single-nerved. The leaf nerves extending beyond the middle of the leaf, but not to the tip to extending to the leaf tip (in the larger, lateral leaves), or extending to the leaf tip (in the smaller, dorsal leaves); of the dorsal leaves somewhat excurrent, or not excurrent. Leaf blade apices pointed; apiculate (in the dorsal leaves), or not apiculate (in the laterals); apically acute, or acuminate. Leaf blade margins flat; unistratose; (crenulate-) denticulate, or entire. Leaf blades not conspicuously bordered. The basal leaf cells more or less isodiametric; irregularly hexagonal; smooth. The walls of basal leaf cells thin to thick; straight. The angular cells not well differentiated. The mid-leaf cells more or less isodiametric; irregularly hexagonal; smooth. The walls of the mid-leaf cells thin to thick; straight.

Plants dioecious.

Sporophyte. Capsules exserted; erect; symmetrical; straight; shortly sub-cylindric; not waisted; neither flattened nor angular; without an externally conspicuous apophysis; with an annulus; without a peristome. The operculum rostrate. Setae long.

Ecology. Confined in Britain to the trunks of the tree fern, Dicksonia antactica. On trunks of the tree fern, Dicksonia antarctica.

British representation. 1 species. Calomnion. Ireland (only in South Kerry).

Classification. Class Bryopsida; Subclass Bryideae; Order Rhizogoniales.

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.’.