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Published In: Species Muscorum Frondosorum 64. 1801. (Sp. Musc. Frond.) Name publication detailView in BotanicusView in Biodiversity Heritage Library

Project Name Data (Last Modified On 10/22/2013)
Acceptance : Accepted
Note : By Richard H. Zander
Project data     (Last Modified On 10/22/2013)
Discussion: The genus, characterized most generally by involute leaf margins, consists of three sections corresponding to degrees of sporophytic reduction: The sect. Weissia shows exserted, operculate capsules with a fairly well-developed peristome. The sect. Hymenostomum lacks a peristome, and the mouth of the capsule, on dehiscence, is covered by an evanescent membrane formed by inner cells of a usually thick capsule wall. The sect. Astomum usually has a short seta, an ovoid to globose, irregularly dehiscent capsule, and no peristome. Weissia differs from Trichostomum in its generally monoicous sexual condition and leaf margins usually incurved or involute. Although Weissia jamaicensis is dioicous, its gametophyte is like that of the monoicous species. Two of the species (now in different sections of the genus) with plane leaf margins, W. sinaloensis and W. planifolia, may be part of a reduction series from an ancestor rather like Trichostomum brachydontium and not from the presumed Weissia jamaicensis-like progenitor of species with usually incurved margins.
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Plants small, caespitose. Stems seldom forked, with a strong central strand and generally a hyaloderm (sometimes poorly differentiated). Leaves tubulose-incurved and contorted when dry, spreading when moist, lingulate to narrowly lanceolate, broadly channeled; margins entire, erect to incurved or involute in the upper 1/2 to 3/4 (rarely plane); costa shortly excurrent as a smooth mucro, with 2 stereid bands and guide cells in 1 layer; upper cells rather small, subquadrate to hexagonal, usually obscured by crowded, bifid papillae; cells of the base smooth, rectangular. Monoicous or rarely dioicous; perichaetia terminal, with inner bracts not much differentiated. Setae very short to elongate; capsules erect, ovoid to short-cylindric; annulus usually present, persistent, consisting of vesiculose cells; operculum usually differentiated, conic to rostrate; peristome none, rudimentary, or well developed and consisting of 16 straight, irregularly cleft teeth.



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