Fissidens rotundifolius Brugg., 2022

Bruggeman-Nannenga, Maria Alida, 2022, Five new species of Fissidens Hedw. (Fissidentaceae, Bryophyta), taxonomic notes and a new species record for South Africa, Cryptogamie, Bryologie 20 (3), pp. 37-49 : 43-46

Fissidens rotundifolius Brugg. -Nann., sp. nov.

( Fig. 5 )

Cryptogamie, Bryologie 43 (2): 28 nomen nudum.

HOLOTYPE. — Tanzania. Hunga Valley below Amani, East Usambara Mts, on bark in rain forest, alt. 860 m, Pócs & Jones s.n. (holo-, EGR, between F. diaphanodontus ; iso-, H. Inoue Bryophyta Selecta Exsiccata no. 580, Fissidens diaphanodontus, EGR , mixed with F. diaphanodontus ).

ETYMOLOGY. — This species is named for its rounded leaf tips (rotundus: rounded; folium: leaf).

ECOLOGY. — On bark in rain forest mixed with Fissidens diaphanodontus .

DESCRIPTION

Stem small, 0.8-1.4 × 0.5-0.8 mm, unbranched, pinnately foliate; rhizoids brown and smooth; axillary nodules not differentiated; leaves close to distant, 9-15 pairs, oblong to lingulate, apex rounded-obtuse, 0.2-0.4(-0.6) × 0.1(-0.2) mm,

2.5-3.5 times as long as wide, margin serrulate, elimbate; limbidium weak (consisting of short, wide cells), reaching 3/4 the length of the vaginant laminae on perichaetial leaves; vaginant lamina ½-³⁄5 the total leaf length, at the insertion narrower than to about as wide the stem, unequal with the minor lamina mostly ending about halfway between margin and costa, unistratose; dorsal lamina slightly rounded at base, reaching the insertion, not decurrent; dorsal and apical lamina unistratose; costa ending 3-9 cells below the apex; lumina of mid dorsal laminal cells 5.5-8.0 × 4.0-6.0 µm, conical; lumina of mid vaginant laminal cells 5.0-9.0 (-10.5) × 4.0-5.5 µm with firm (1.5 µm wide), mammillose walls. Gemmae not seen.

Perigonial stems (one seen) on rhizoids at the base of a vegetative stem, 0.5 mm tall, short, budlike, perigonial branches also present, antheridia 100-130 µm long; perichaetia terminal; perichaetial leaves 0.5-1.3 mm long; archegonia 190-230 µm long; calyptra not seen.Sporophyte: seta ± 1 mm long, smooth, 1 per perichaetium, capsule erect, 0.35 × 0.1. 5 mm, with 22-32 columns of oblong exothecial cells around the capsule; peristome poorly developed, stiff, genu-inflexed when wet, teeth undivided, short, ±60-100 µm long, tooth base 18-28.5 µm wide, basal 4 OPL cells with high, thin, smooth trabeculae, lamellae hard to observe, probably smooth, distal part densely papillose; operculum not seen; spores subglobose, 19-21.5 × 17-19 µm, papillose.

This corticolous species is characterized by its small size, wide oblong-lingulate leaves with rounded obtuse tips, distally spurred costae that end 3-9 cells below the apex, firm-walled laminal cells that appear smooth but are mammillose, and undivided peristomes. If it were not for its peristome this species could be taken for a young expression of some larger species like F. punctulatus Sande Lac. , F.diaphanodontus (P.de la Varde) Bizot or F. alomoides Müll.Hal. ex Dusén. These species likewise have oblong-lingulate leaves, short costae, mammillose laminal cells and limbidia that are more or less restricted to the perichaetial leaves. These species, however, are all larger, have longer leaves and different peristomes. Peristomes are anomalous in the first two, whereas F. alomoides has scariosus- type peristomes. For figures of the peristomes of F. diaphanodontus and F.punctulatus see Bruggeman-Nannenga 2022 (figs 6, 16). Expressions of F. serratus Müll.Hal. with oblong leaves can be separated from the new species by their distinctly serrulate margins (coarsely serrulate on the basal part of the vaginant laminae), whereas F. hymenodon Besch. has slightly longer leaves and 1-2 papillose laminal cells. Both F. serratus and F. hymenodon have scariosus - type peristomes.

Figures

FIG. 5. — Fissidens rotundifolius, sp. nov. A, sporophytic stem; B, vegetative stem; C, perichaetial stem with apical proliferation; D, perigonial stem; E, leaf; F, basal part of four peristome teeth (OPL),showing the genuflexed base and OPL trabeculae;G, peristome tooth exterior side (OPL); H, peristome tooth interior side (IPL) (all from holotype). Scale bars: A-D, 0.5 mm; E, F, 50 µm; G, H, 20 µm.