7. Pogonatum P. Beauvois, Mag. Encycl. 5: 329. 1804.
[Greek pogon, beard, alluding to hairy calyptra]
Gary L. Smith Merrill
Plants medium to large, in loose pure tufts or growing among other bryophytes, or individual stems small and scattered over a persistent protonemal mat. Stems simple or branched by subfloral innovations. Leaves with a sheathing base merging gradually or ± abruptly contracted to the blade, the sheath entire (toothed in P. contortum), with or without incrassate hinge-cells at the shoulders, not hyaline-margined (except in P. urnigerum); margins serrate, toothed, or entire, without a differentiated border of elongated cells; adaxial lamellae numerous and compact, occupying the full width of the blade, or somewhat fewer with an evident marginal lamina, marginal cells not differentiated, or strongly differentiated, thick-walled and coarsely papillose. Sexual condition dioicous; male plants similar to females in appearance, or bud-like and inconspicuous. Seta smooth. Capsule ovoid to short-cylindric, ± regular to somewhat asymmetric, terete, sometimes with 4 or more indistinct angles or ridges; hypophysis not differentiated, tapering; stomata none; exothecium mammillose to scabrous, the exothecial cells mamillate or with a single papillate projection of the outer wall; operculum rostrate from a convex base; epiphragm persistent, attached to the peristome teeth; peristome deeply reddish pigmented (at least in the median line), the teeth 32, compound, with median sinus narrow or almost obliterated. Calyptra with a densely matted felt of hairs, covering most or all of the capsule. Spores finely papillose.
Species 52 (5 in the flora): North America, tropical America, Europe, Africa, Asia, Australasia, widespread in the tropics of both hemispheres, with only a few North temperate representatives.
North American species of Pogonatum vary greatly in size and habit from tall, laxly tufted plants to protonema mosses with individual plants scattered and only a few millimeters high. Pogonatum contortum of the Pacific Northwest, with leaves strongly crisped and contorted when dry, is the most “typical” of the genus as a whole. Pogonatum brachyphyllum and P. pensilvanicum are protonema-mosses, the gametophyte consisting of a persistent felted mat of protonema and leafy plants small and scattered. The other two species are distinctly polytrichoid in habit, with the margins of the lamellae thick-walled and coarsely papillose. Pogonatum dentatum is an arctic-montane species, whereas P. urnigerum has a somewhat more southerly distribution and occurs as well in the Himalayas and New Guinea. The sporophytes of our species are more uniform, with a scabrous exothecium, deeply pigmented peristome with compound peristome teeth, and no stomata. The exothecial “papillae” are projections of the cell wall, unlike the wart-like cuticular papillae often seen on the leaf surfaces of many Polytrichaceae.
SELECTED REFERENCE
Hyvönen, J. 1989. A synopsis of genus Pogonatum (Polytrichaceae, Musci). Acta Bot. Fenn. 138: 1-87.
