Monographs Details: Fissidens saülensis Pursell & W.R.Buck
Authority: Pursell, Ronald A. 2007. Fissidentaceae. Fl. Neotrop. Monogr. 101 (Published by NYBG Press)
Family:Fissidentaceae
Description:Species Description - Plants dark green, persistent protonemata frequent. Stems monomorphic, unbranched, 2-5 mm long x 1.5-2.5 mm wide; rhizoids basal, smooth, tan; axillary hyaline nodules not differentiated; epidermis and outer 1-2 tiers of cortical cells small, incrassate, pigmented; inner cortical cells larger, thin-walled, hyaline; central strand absent. Leaves ± crispate ± parallel to costa when dry, distant to loosely imbricate, as many as 10 pairs, oblong, obtuse, apex usually asymmetric, 0.8-1.7 mm long x 0.2-0.4 mm wide; margin crenulate-serrulate, limbate and entire in proximal parts of most vaginant laminae, limbidium weak, limbidial cells unistratose; costa long-excurrent, bryoides type; dorsal lamina rounded to insertion, not decurrent; vaginant laminae of cauline leaves 2/5 leaf length, acute, unequal, minor lamina ending about midway between costa and margin; laminal cells distinct, guttulate, unistratose, smooth, slightly bulging, irregularly quadrate to hexagonal, 9-22 µm long, somewhat smaller at margin, larger and oblong-hexagonal to oblong juxtacostally. Monoicous (rhizautoicous); gemmiform perigonial stems scattered on protonemata among infertile and perichaetial stems; perichaetia terminal. Sporophytes 1 per perichaetium, yellow, darkening with age; seta smooth, 2 mm long; theca exserted, erect, radially symmetric, 0.5 mm long, stomatose, exothecial cells quadrate, collenchymatous; peristome scariosus type. Operculum, spores, and calyptra not seen.

Discussion:Fissidens saülensis and F subulatus share a suite of characters, including persistent protonemata, a long-excurrent costa, an asymmetric leaf apex, and a weak limbidium. The best distinctions between the two species are found in the leaves. Fissidens saülensis has oblong leaves in which the dorsal lamina extends to the insertion, whereas F. subulatus has lanceolate leaves in which the dorsal lamina usually ends well above the insertion. Moreover, the median laminal cells of F. saülensis are smaller than those in F. subulatus (9-22 µm vs. 12-30 µm, respectively). In addition, the laminal cells of F. saülensis are guttulate while those of F subulatus are eguttulate. Lastly, plants of F. saülensis are usually larger with a greater number of leaves.

Fissidens saülensis might be confused also with F. pellucidus. Both species have guttulate, regularly hexagonal laminal cells. However, while F saülensis usually has persistent protonemata, these structures are absent from F. pellucidus. Moreover, a limbidium in F. saülensis is found on the vaginant laminae of most or all leaves, but occurs only infrequently on the vaginant laminae of perichaetial leaves in F. pellucidus. The leaf apex of F. saülensis is asymmetric while that of F. pellucidus is more or less symmetric except in the expression with excurrent costae.
Distribution:Trinidad and Tobago South America| Sipaliwini Suriname South America| Cayenne French Guiana South America| Chocó Colombia South America|