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| The moss families (Bryophyta, Musci) of Britain and Ireland |
White-mosses.
~Dicranaceae
Gametophyte. Plants “normal”, with leaves containing chlorophyll. Acrocarpous; cushion-forming (the cushions characteristically large, compact and rounded, glaucous or albescent). Mature plants 100–500 mm high. The leaves of main stems and branches similar in form (with a very peculiar and characteristic anatomical layout). The leaves leucobryoid (three or more layered, with a median, open network of long and narrow chlorophyllous cells, sandwiched between layers of much larger, empty, hyaline cells. The latter are interconnected by conspicuous pores, and some have openings to the outside, endowing the leaves with a sponge-like capacity to absorb and retain water. They are analogous in this respect with branch leaves of the unrelated Sphagnum, but lack the spiral wall thickenings characteristic of them). The leaves ovate to narrowly lanceolate; spiral; (sub-) secund (especially when moist), or not secund; crisped when dry, or not crisped when dry; at least theoretically, single-nerved (in that the greater part seems to represent nerve (cf. Polytrichum), the vestigial lamina being represented by its narrow margins). The leaf nerves extending to the leaf tip. Leaf blade apices pointed; acuminate; conspicuously hyaline, or not hyaline. Leaf blade margins entire. Leaf blades bordered. The basal leaf cells somewhat longitudinally elongated to longitudinally much elongated; rectangular; smooth. The walls of basal leaf cells thin; straight. The angular cells not well differentiated. The mid-leaf cells somewhat longitudinally elongated to longitudinally much elongated; rectangular (if the laminate component of the leaf is not regarded as entirely basal); smooth. The walls of the mid-leaf cells thin; straight.
Plants dioecious.
Sporophyte. Capsules exserted; erect to inclined; symmetrical to asymmetrical; weakly to strongly curved; clavate (slightly), or sub-cylindric to ellipsoid, or ovoid, or pyriform, or gibbous; with an externally conspicuous apophysis to without an externally conspicuous apophysis; striate and becoming regularly furrowed when dry and empty; dehiscing via a lid; with a peristome. The peristome single. The peristome teeth 16; not grouped; deeply cleft; perforated; thin, membranous, and transversely barred; interiorly exhibiting a fine longitudinal dividing line between the transverse bars. The operculum rostrate. Setae 8–18 mm long; straight, or curved.
Ecology. Occurring in acid conditions. On soil, rocks, tree stumps, in wet or dry locations, sometimes in bogs.
Cytology. Haploid chromosome number, n = 11 (in L. glaucum).
Representation in Britain and Ireland. 2 species. Leucobryum. 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 Dicranideae; Order Dicranales.
Illustrations. • Leucobryum juniperoideum and L. glaucum: Dixon. LEUCOBRYACEAE: A, Leucobryum juniperoideum (Brid.) C. Mull.; B, Leucobryum glaucum (Hedw.) Ångstr.
From Dixon and Jameson (1924), the unscaled screen display approximately doubling the magnifications given with their individual figures. 1, leaf or stem leaf where these differ; 2, branch-leaf; 3, perichaetial leaf; 4, perigonial leaf; 5, capsule; 6, peristome; 7, calyptra; 8, spores; 9, inflorescence; 10, gemmae; 11, paraphyllia; 12, stoma of capsule; *, plant, or part of one. Qualifications: a, apex; b, base; c, cells at one third from the apex; cv, ventral aspect of cells; cd, dorsal aspect of cells; bc, basal cells; x, section. • Leucobryum (with assorted dicranoid taxa): Berkeley. LEUCOBRYACEAE: 6, Leucobryum glaucum (Hedw.) Ångstr.; a, habit; b, leaf; c, leaf tip; d, capsule; e, part of peristome. DITRICHACEAE: 5, Ceratodon purpureus (Hedw.) Brid.; a, habit; b, leaf, c, capsule; d, part of peristome; e, detail of peristome tooth tip. DICRANACEAE: 4, Campylopus flexuosus (Hedw.) Brid.; a, habit; b, leaf; c, calyptra; d, capsule. 7, Dicranum scoparium Hedw.; a, habit; b, leaf; c, part of peristome. 8, Dicranella heteromalla (Hedw.) Schimp.; a, habit; b, leaf; c, capsule; d, part of peristome. 10, Arctoa fulvella (Dicks.) R. Br.; a, habit; b, leaf; c, capsule; d, part of peristome. RHABDOWEISIACEAE: 9, Oreoweisia bruntonii (Sm.) Milde; a, habit; b, leaf; c, capsule; d, part of peristome.
From Berkeley (1863, Plate 23). The approximate 1 cm scale applies to the whole plant (habit) illustrations only.
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, 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. See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2005 onwards. The moss families (Bryophyta, Musci) of Britain and Ireland. Version: 5th August 2019. delta-intkey.com’.
