Monographs Details: Fissidens palmatus Hedw.
Authority: Pursell, Ronald A. 2007. Fissidentaceae. Fl. Neotrop. Monogr. 101 (Published by NYBG Press)
Scientific Name:Fissidens palmatus Hedw.
Synonyms:Dicranum palmatum (Hedw.) F.Weber & D.Mohr, Skitophyllum palmatum (Hedw.) Bach.Pyl., Conomitrium palmatum (Hedw.) Müll.Hal., Conomitrium reticulosum Müll.Hal., Fissidens reticulosus Mitt., Fissidens sphagnifolius Sull.
Description:Species Description - Plants pale to bright green. Stems monomorphic, unbranched, 2-4 mm long x 2-3.5 mm wide; rhizoids basal and lateral, smooth, light tan; axillary hyaline nodules absent; epidermis and smaller but little differentiated from cortical cells, all thin-walled, thickening with age; central strand present or absent. Leaves crispate when dry, loosely imbricate, usually arranged palmately, as many as 7 pairs, lanceolate to oblong-lanceolate, acute to obtuse-apiculate or short-acuminate, to 2.8 mm long x 0.4-0.5 mm wide; margin entire, serrulate-crenulate at apex, limbate, limbidium on all laminae, reaching apex or ending slightly below, sometimes ± difficult to recognize, limbidial cells uni- and bistratose; costa ending as many as 25 cells below apex to percurrent, narrowed and often forked distally, bryoides type, sometimes reduced in structure; dorsal lamina narrowed proximally, often rounded at insertion, not decurrent; vaginant laminae ± 1/2 leaf length, acute, ± equal; laminal cells distinct, eguttulate, thin-walled, smooth, plane to bulging, mostly 22-104 µm long x 13-31 µm wide, juxtacostal cells largest, juxtalimbidial cells smallest. Monoicous (gonioautoicous and rhizautoicous); perigonia gemmiform, axillary or at base of infertile and perichaetial stems; perichaetia terminal on stems. Sporophytes 1-2 per perichaetium, yellow, darkening with age; seta smooth, 4-11.5 mm long; theca exserted, inclined to horizontal, ± arcuate, bilaterally symmetric, 0.40.7 mm long, stomatose, exothecial cells quadrate to oblong, collenchymatous, vertical walls thicker that horizontal walls; peristome scariosus type; operculum conic, long-rostrate, 0.3-0.7 mm long. Spores smooth, 9-14 µm. Calyptra cucullate, smooth, 0.40.7 mm long.

Discussion:Fissidens palmatus is distinguished by its palmately arranged, lanceolate to oblong-lanceolate leaves, large, thin-walled laminal cells, weak limbidium, and bilaterally symmetric theca. The limbidium in some specimens, e.g., Buck 23400 from Cuba, is poorly developed so that the plants could be interpreted as elimbate. The costa is also quite variable in length, as it is in other related species. Those expressions with a costa that ends well below the apex were formerly known as F. reticulosus. The species might be confused with F. dissitifolius but this species differs by its pinnately arranged lanceolate leaves, smaller laminal cells, and erect thecae.
Distribution:Saint-Laurent-du-Maroni French Guiana South America| Trinidad and Tobago South America| Tabasco Mexico North America| Veracruz Mexico North America| Panamá Panama Central America| Piñar del Río Cuba South America| Sancti Spíritus Cuba South America| Jamaica South America| Samaná Dominican Republic South America| Puerto Rico South America| Monagas Venezuela South America| Rupununi Guyana South America| Acre Brazil South America| Pará Brazil South America| Beni Bolivia South America|