Monographs Details: Fissidens prionodes Mont.
Synonyms:Fissidens marmellensis Broth.
Description:Species Description - Plants light green, becoming rust-colored, particularly in stems and costae. Stems monomorphic, unbranched to sparingly branched, 3.0-6.0 mm long x 1.00-2.25 mm wide; rhizoids basal, smooth, reddish; axillary hyaline nodules absent; epidermis and outer 1-3 tiers of cortical cells small, incrassate, pigmented; inner cortical cells larger, thin-walled, hyaline; central strand present. Leaves little changed when dry, distant to loosely imbricate, as many as 16 pairs, narrowly lanceolate, sharply acute, to 1.8 mm long x 0.2-0.3 mm wide, perichaetial leaves longest; margin sharply serrulate, elimbate; costa excurrent, with ± obsolete serrations, bryoides type; dorsal lamina narrowed proximally, ending at insertion or above; vaginant laminae of cauline leaves ± 1/2 leaf length, unequal, minor lamina either rounded and free distally or acute, narrowed and ending near costa or near margin; laminal cells distinct, eguttulate, frequently irregularly bistratose, firm-walled, mammillose, irregularly quadrate to hexagonal, 8-15 µm long, juxtacostal cells in proximal parts of vaginant laminae smooth, most narrowly linear, 16-61 µm long. Monoicous (rhizautoicous); perigonial stems gemmiform, basal, or to 1.5 mm long with 6 pairs of leaves. Sporophytes 1-2 per perichaetium, yellow, darkening with age; seta smooth, 3.0-5.5mm long; theca exserted, erect, radially symmetric, 0.6 mm long, stomatose, exothecial cells ± quadrate, collenchymatous; peristome scariosus type; operculum conic, long-rostrate, 0.5 mm long. Spores smooth, 7-11 µm diam. Calyptra cucullate, smooth, 0.4 mm long.
Discussion:Fissidens prionodes is characterized by narrowly lanceolate, sharply acute, elimbate leaves, excurrent costa, strongly mammillose laminal cells, and sporophytes terminal on main stems. It is close to F. allionii, which has similar laminal cells. In F. allionii, however, the costa is much thicker and broader, and is usually only percurrent, and the sporophytes are mostly borne terminally on short axillary branches. Small perigonial stems, not observed in F. allionii, are present in F. prionodes.
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