The Moss Families of the British Isles

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L. Watson and M. J. Dallwitz

Amphidiaceae

Yoke-mosses.

~Dicranaceae, Rhabdoweisiaceae.

Gametophyte. Acrocarpous; densely cushion-forming. Mature plants to 40–80 mm high. Stems not tomentose; with a differentiated central strand. The leaves of main stems and branches similar in form; lanceolate to linear, or lingulate; not distichous; spiral; not secund; crisped when dry. Leaf bases not sheathing; not decurrent. 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; not excurrent; incorporating stereids, or without stereids. Leaf blade apices pointed; not apiculate; apically acute, or acuminate; not hyaline. Leaf blade margins revolute or recurved (on one or both sides); unistratose; distally denticulate, or entire. Leaf blades not conspicuously bordered. The basal leaf cells somewhat longitudinally elongated to longitudinally much elongated; rectangular; smooth. The walls of basal leaf cells thin, or thick; straight. The angular cells not well differentiated. The mid-leaf cells more or less isodiametric; hexagonal to rounded; papillose. The walls of the mid-leaf cells thick; straight.

Plants monoecious, or dioecious (in A. mougeotii); in A. lapponicum, autoecious. Parapyhyses absent.

Sporophyte. Capsules emergent to exserted; erect; symmetrical; straight; narrowly pyriform; not waisted; without an externally conspicuous apophysis; striate and becoming regularly furrowed when dry and empty; without an annulus. Calyptra splitting down one side. Capsules dehiscing via a lid; without a peristome. Setae present; very short; straight.

Ecology. Mesophytic and xerophytic; occurring in basic habitats (A. lapponicum), or neutral pH conditions, or acid conditions (A. mougeotii). On cliffs and rock outcrops or in crevices, in ravines and woods, coastal and inland.

Cytology. Haploid chromosome number, n = 13 (A. lapponicum).

British representation. 2 species. Amphidium. Northern Scotland, southern Scotland, northern England, Wales, southwest England, and Ireland.

Classification. Class Bryopsida; Subclass Dicranideae, or Bryideae; Order Dicranales, or Orthotrichales.

Illustrations. • Zygodon, with Amphidium: Dixon.


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. http://delta-intkey.com’.

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