The Taxonomic Status of the Nanobryaceae (Bryopsida)

Abstract

The family Nanobryaceae Schultze-Motel and the genus Nanobryum Dix. are synonyms of Fissidentaceae Schimp. and Fissidens Hedw., respectively. Fissidens gladiolus Mitt. ( Nanobryum gladiolum (Mitt.) Biz.) is illustrated. Our study (Pursell & Reese 1980) of Fissidens subulatus Mitt., a species recently rediscovered in Brazil, prompted us to review the taxonomy of the African family Nanobryaceae Schultze-Motel (1969) (= Archifissidentaceae Dix. & P. de la Varde, nom. illeg.), which consists of a single highly variable species, Nanobryum gladiolum (Mitt.) Biz. (= N. duemmeri Dix., fide Bizot 1963). Dixon (1922) was unsure of the relationship of Nanobryum when he described it as a new genus for N. duemmeri from Uganda and from Cape Province, South Africa. Although Dixon recognized that the peristome of Nanobryum was similar to those of some species of Fissidens, his oversight of the short, narrow dorsal and ventral laminae on some leaves led him to suggest an affinity with either Seligeria or Dicranella; he assigned his new genus to the Dicranaceae. Potier de la Varde (1927), however, arrived at a better evaluation of the vegetative plant when he and Dixon established the family Archifissidentaceae to accommodate Nanobryum as an ancestral form of Fissidens. The family Archifissidentaceae is based wholly on two character states-linear to rhombo-linear laminal cells and persistent protonemata. In view of the variation in these characteristics presently found within the Fissidentaceae, there appears to be insufficient justification to warrant continued recognition of the family Nanobryaceae and the genus Nanobryum. For example, the diminutive plants of F. exilis Hedw. are formed amidst persistent protenemata. Also, the somewhat elongated leaf cells of Nanobryum do not seem unusual when one considers the wide range of laminal cells found in Fissidens, e.g., the small, pluripapillose, isodiametric cells of F. elegans Brid., the smooth, thin-walled, oblong-hexagonal cells of F. mollis Mitt., and the elongated, prosenchymatous cells of F. scariosus Mitt. As recognized by Potier de la Varde (1927) and later by Bizot (1963), the leaf form of Nanobryum does not differ basically from that of Fissidens, i.e., it consists of two vaginant laminae, a dorsal lamina, and a ventral lamina. Admittedly, the last two are not always present in Nanobryum, but neither are they always expressed in all leaves in Fissidens. Thus, the continued distinction of Nanobryum from Fissidens is unwarranted. We propose that Nanobryaceae and Nanobryum be considered synonyms of Fissidentaceae and Fissidens, respectively. 007-2745/80/559-562$0.65/0 This content downloaded from 157.55.39.143 on Wed, 15 Jun 2016 06:54:13 UTC All use subject to http://about.jstor.org/terms TABLE 1. Comparison of sporophytes of Fissidens gladiolus Mitt., Nanobryum duemmeri Dix., and Anisothecium pallidisetum P. de la Varde. Length (mm) Length of and attitude setae (mm) of thecae Peristome teeth Opercula Spores (/Lm) F. gladiolus 3.5 _0.51, finely papillose conic-rostratel not seen (M. P rk, isotype) horizontal (distal parts br ken) N. duemmeri (Wager +2.4-3.5 ?0.46-0.53, finely papillose not seen smooth, 12-16 955, paratype) horizontal (distal parts broken) N. duemmeri (Diimmer -4.5 +0.57, finely papillose proximally, not seen smooth, 11 4080a, lectotype) horizontal spirally thickened distally N. duemmeri (Crosby -3.5-7.0 +0.45-0.53, finely papillose proximally, conic-rostrate smooth, 11-14 et al. 8749) horizontal spirally thickened distally A. pallidisetum2 4 _0.50, loosely papillose conic-rostrate smooth, 15 horiz ntal (cruribus axe papillosis) (alto-conicum) 1 Absent from plant comprising the isotype but illustrated in the protologue. 2 Specimen not seen; information taken from the protologue. ?A 0 O