Monographs Details: Weissia
Authority: Sharp, Aaron J., et al. 1994. The Moss Flora of Mexico. Part One: Sphagnales to Bryales. Mem. New York Bot. Gard. 69 (1)
Family:Pottiaceae
Scientific Name:Weissia
Description:Species Description - Plants small, caespitose. Stems seldom forked, with a strong central strand and generally a hyaloderm (sometimes 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 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.

Discussion:

The genus, characterized most generally by involute leaf margins, consists of three sections corresponding to degrees of sporophytic reduction: T h e 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 usually incurved or involute leaf margins. Although Weissia jamaicensis is dioicous, its gametophyte is like that of the monoicous species. T w o 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.