Monographs Details: Fissidens subulatus Mitt.
Synonyms:Conomitrium subulatum (Mitt.) A.Jaeger, Fissidens validicostatus Sull.
Description:Species Description - Plants pale green to castaneous, scattered among persistent protonemata. Stems monomorphic, unbranched, 3 mm long x 1.25 mm wide; rhizoids basal, 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, ± rolled inward longitudinally toward costa when dry, as many as 5 pairs, lanceolate, acute, apex often asymmetric, to 1.5 mm long x 0.2 mm wide, perichaetial leaves largest, lower leaves small, scale-like, typically lacking dorsal and ventral laminae; margin entire to crenulate-serrulate, marginal cells of vaginant laminae ± elongate, forming a weak, inconspicuous limbidium, limbidial cells unistratose; costa mostly long excurrent, bryoides type; dorsal lamina, ending well above insertion; vaginant laminae of cauline leaves ±1/3 leaf length, unequal, minor lamina usually narrowed above, ending on costa, broad and retuse in perichaetial leaves; laminal cells distinct, eguttulate, unistratose, firm-walled, smooth, mostly oblong, oblong-hexagonal and rhombic, 12-30 pm long x 718 pm wide, marginal cells smaller, 9-13 pm long, juxtacostal cells in vaginant laminae larger, 31-43 µm long x 11 pm wide. Monoicous (rhizautoicous); perigonial stems gemmiform, around base of perichaetial stems; perichaetia terminal on stems. Sporophytes 1-2 per perichaetium, yellow, darkening with age; seta smooth, 1.5-4.0 mm long; theca exserted, erect, radially symmetric to ± inclined, bilaterally symmetric, 0.3-0.5 mm long, stomatose, exothecial cells quadrate, collenchymatous; peristome scariosus type; operculum conic, long-rostrate, 0.4 mm long. Spores smooth, 7-11 µm diam. Calyptra cucullate, smooth, 0.5 mm long.
Discussion:Stems of this small Fissidens grow scattered among persistent protonemata. Few leaves are produced on each stem, and the lower ones are generally small and scale-like, lacking both ventral and dorsal laminae. On other leaves, the dorsal lamina is typically poorly developed. When observed in the field, the long-excurrent costae give the plants a Di-cranella-like appearance. Sporophytes are usually abundant, otherwise the plants could be easily overlooked. The species is most apt to be confused with F. ornatus. In both species the costa is characteristically long-excurrent from an asymmetric leaf apex, and the laminal cell are dimorphic, the inner cells much larger than the marginal cells. In F. ornatus, however, the dorsal lamina is usually well developed, and persistent protonemata are rare.
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