Monographs Details: Fissidens geijskesii Florsch.
Authority: Pursell, Ronald A. 2007. Fissidentaceae. Fl. Neotrop. Monogr. 101 (Published by NYBG Press)
Description:Species Description - Plants bright green at growing tips, blackish-green below. Stems monomorphic, to 100 mm [10 cm] long x 2-3 mm wide, profusely branched; rhizoids basal and axillary, reddish; axillary hyaline nodules absent; epidermis and outer 2-4 tiers of cortical cells small, incrassate, pigmented; inner cortical cells larger, thin-walled, hyaline; central strand absent. Leaves little changed when dry, imbricate, in many pairs, lanceolate, acute, to 2.7 mm long x 0.5 mm wide; margin entire, elimbate; costa distinct, ending several cells below leaf apex, taxifolius type; dorsal lamina ending at insertion or short-decurrent; vaginant laminae of cauline leaves ± 2/3 leaf length, acute, ± equal, minor lamina ending on or very near margin; laminal cells distinct, eguttulate, regularly bistratose to pluristratose, uni-to bistratose in vaginant laminae, firm-walled, irregularly quadrate to rounded-hexagonal, surface cells smooth, plane, 10-18 µm long. Monoicous (gonioautoicous); perigonia gemmiform, axillary, numerous; perichaetia terminal on stems and branches. Sporophytes 1 per perichaetium, numerous, reddish; seta smooth, short, 0.2-0.4 mm long; theca immersed to emergent, erect, radially symmetric, 0.6-0.7 mm long, estomatose, exothecial cells quadrate to oblong, ± collenchymatous, vertical walls slightly thicker than transverse walls; peristome anomalous, fragile, undivided to irregularly divided, filaments reduced, papillose; operculum conic, short-rostrate, 0.3 mm long. Spores not seen, according to protologue, 30-36 µm diam. Calyptra mitrate, smooth, 0.5 mm long.

Discussion:Gametophytically, Fissidens geijskesii is similar to F. grandifrons; both species are aquatic, profusely branched, and have imbricate lanceolate leaves in which the laminal cells are pluristratose. Whereas F geijskesii has a typical aquatic sporophyte, i.e., very short seta, capsule immersed to emergent, the sporophyte of F grandifrons is typically terrestrial, i.e., the capsule is elevated well above the gametophyte on an elongate seta. Moreover, the costa in F. geijskesii is easily discerned throughout its length while the costa of F. grandifrons is difficult to recognize from the surface. Some expressions of F. rochensis approach F. geijskesii and F. grandifrons in appearance, but the leaves in this species are limbate.
Distribution:Suriname South America|