Plagiochila barteri Mitt.

Gradstein, S. Robbert & Reeb, Catherine, 2022, The genus Plagiochila (Dumort.) Dumort. (Marchantiophyta) in Madagascar, Cryptogamie, Bryologie 20 (5), pp. 65-106 : 70-72

Plagiochila barteri Mitt.

( Fig. 2 )

Plagiochila barteri Mitt. , Journal of the Linnean Society, Botany 22: 320 (1886). — Type: Sierra Leone. Barter s.n. (holo-, NY; fide Grolle 1995).

SPECIMENS EXAMINED. — Madagascar. “Mts. Morojezy”, 1300 m, Guillaumet 4150 ( PC). — Prov. Antsiranana • Manongarivo-Ambahatra Reserve, ridge of Ambahatra Mt., III.1999, Geissler 19460/1 ( EGR, G) .

A B C F D E G

DISTRIBUTION AND HABITAT. — Widespread in the mountains of tropical Africa. In Madagascar apparently rare, found twice on rotten wood in humid mid-elevation forest, 850- 950 m. Further Madagassan records belong to P. sikorae .

DESCRIPTION (see also Jones 1962; Vanden Berghen 1981) Plants rather robust, 3-5 mm wide, to 10 cm long, unbrached or with a few short branches, all branches intercalary, rhizome -like creeping shoot present, dorsal stem surface without paraphyllia. Mature stem leaves imbricate, obliquely to widely spreading, asymmetrically and narrowly elongate-triangular, c. 2-2.5× longer than wide, widest at the base, ampliate, the ventral bases forming a high crest, apex ± truncate, margins frequently bordered by thicker-walled cells, with 20-50 teeth, apex with 2-3short teeth, ventral margin with 10-25 linear teeth, dorsal margin with 2-15 teeth and dorsal base with 2-8 teeth, the teeth 1-6 cells long and usually longest at the ventral leaf base, made up of quadrate to narrowly rectangular cells, the tip cell strongly elongate; dorsal base longly and broadly decurrent, the decurrent part swollen concealing the stem, ventral base shortly and narrowly decurrent, the decurrent linear portion to 0.1 mm long. Leaf cells isodiametrical to somewhat elongate, 20-25 µm wide in midleaf, with large, trabeculate trigones, often more strongly thickened towards the leaf margin and forming a border, leaf base with a short vitta-like area, cells in the dorsal leaf base frequently elongate; cuticle smooth; oil bodies not observed. Underleaves absent. Androecia terminal to intercalary. Perianth base covered by bracts, perianth mouth longly ciliate-laciniate.Vegetative reproduction by leaf fragmentation.

NOTES

Plagiochila barteri (sect. Africanae Heinrichs) is a robust species that is recognized by purely intercalary branching and wide-spreading, narrowly ovate-triangular leaves with toothed dorsal leaf bases and strongly ampliate ventral bases. The dorsal leaf bases are longly and broadly decurrent and ± concealing the stem, the leaf margins have 20-50 linear teeth with a stronly elongate tip cell, and the leaf cells are rather small, 20-25 µm wide in midleaf, with large trigones and sometimes forming a border of thicker-walled cells, and being elongate in the dorsal leaf base. A variety with subentire and rather short and broad, conspicuously bordered leaves, P. barteri var. valida (Steph.) Vanden Bergh. (lecto-, designated here: La Réunion, 1889, Rodriguez 38, G00068917!), occurs in the Mascarenes ( Vanden Berghen 1981) and may be expected to occur in Madagascar.

Plagiochila sikorae Steph. was treated as a synomym of P. barteri by Vanden Berghen (1981) but is here restored as a good species, differing from P. barteri in the presence of paraphyllia on the dorsal stem surface and ± falcato-secund leaves with fewer teeth (less than 20). Most specimens from Madagascar cited inVanden Berghen (1981) under the name P. barteri belong to P. sikorae .

Figures

FIG. 2. ― Plagiochila barteriMitt.: A, habit; B, shoot with intercalary branch;C, shoot in dorsal view;D, leaves,showing the presence of teeth at the dorsal leaf base; E, upper part of leaf; F, G, midleaf cells; H, leaf margin. From Geissler 19460 (EGR).Scale bars: A, 2 mm; B, C, E, H, 0.5 mm; D, 1 mm; F, 0.05 mm; G, 0.025 mm.