Monographs Details: Fissidens townsendianus Pursell
Synonyms:Fissidens weirii var. insertus Grout
Description:Species Description - Plants green to yellow-green. Stems monomorphic, unbranched and branched, to 7 mm long x 2.5 mm wide; rhizoids basal and axillary, smooth, reddish; axillary hyaline nodules absent; epidermis and outer 1-2 tiers of cortical cells small, incrassate, pigmented; inner cortical cells larger, thin-walled, hyaline; central strand absent. Leaves crispate when dry, loosely imbricate, as many as 11 pairs, oblong to lanceolate, acute to obtuse-cuspidate, to 1.8 mm long x 0.4 mm wide; margin serrulate, limbate, limbidium marginal on vaginant laminae, intralaminal on dorsal and ventral laminae, bordered by 1-4 rows of cells, ending well above insertion of dorsal lamina and below apex, usually spurred, limbidial cells bi- to quadristratose; costa ending in cusp or 2-4 cells below apex, bryoides type; dorsal lamina truncate to rounded at insertion, not decurrent; vaginant laminae of cauline leaves ± 1/2 leaf length, acute, ± equal; laminal cells obscure, eguttulate, unistratose, firm-walled, pluripapillose, quadrate to hexagonal, 5-7 µm long. Monoicous (gonioautoicous); perigonia gemmiform, axillary; perichaetia terminal on stems and branches. Sporophytes 1 per perichaetium, yellow, darkening with age; seta smooth, to 2.5 mm long; theca exserted, erect, radially symmetric, 0.5-0.6 mm long, stomatose, exothecial cells quadrate to oblong, collenchymatous, vertical walls thicker than horizontal walls; peristome scariosus type or sometimes reduced with short filaments, coarsely papillose, efimbriate; operculum not seen. Spores finely papillose, 13-18 µm diam. Calyptra not seen.
Discussion:Fissidens townsendianus is distinguished best by its bi- to quadristrastose, intralaminal limbidium on the dorsal and ventral laminae. Fissidens neglectus and some expressions of F. elegans also have an intralaminal limbidium, but in these species the limbidium is restricted to the vaginant laminae and the limbidial cells are unistratose. The peristome, of which only two have been seen, appears to be variable, in one specimen it is a typical scariosus type, while in the second it is reduced, as described above. The holotype of F. weirii var. insertus upon which F. townsendianus, nom. nov:, is based, could not be located. However, the small, obscure, pluripapillose laminai cells, and the intralaminal limbidium of the dorsal and ventral laminae leave not doubt about the taxon that Grout described.
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