Plagiochila sikorae Steph.

Gradstein, S. Robbert & Reeb, Catherine, 2022, The genus Plagiochila (Dumort.) Dumort. (Marchantiophyta) in Madagascar, Cryptogamie, Bryologie 20 (5), pp. 65-106 : 92-94

Plagiochila sikorae Steph.

( Fig. 17)

Plagiochila sikorae Steph. , Bulletin de la Société royale de Botanique de Belgique 32 (2): 37 (1893). — Type: Madagascar. Without locality, 1891, Sikora 85 p. p., c. andr. (holo-, G00045519!).

ADDITIONAL SPECIMENS EXAMINED. — Madagascar. Prov. Antsiranana • Manongarivo-Ambahatra Reserve, ridge between the two branches of Ambahatra Mt., 850-950 m, III.1999, Geissler 19459 ( EGR, G, GOET); Marojejy Nat. Park , elfin forest on ridge, 1000- 1400 m, III.1990, Pócs et al. 90114/DC ( EGR as P.repanda ). — Prov. Fianarantsoa • Andringitra Nat. Park, Ambavafatra, heath forest at the N foot of Mt. Vohipia , 1270-1350 m, IX.1994, Pócs 9477/D, c.gyn. ( EGR); Ranomafana Nat. Park , E. ridge of Mt. Vohipanani , 1140-1230 m, VII.2003, Pócs & Ranaivojaona 04121/ CS ( EGR); Namorona river , 1080-1150 m, VII.2003, Pócs & Ranaivojaona 04126/ AT ( EGR, GOET). — Prov. Toamasina • pont Sanjouin between Moramanga and Anosibe, 900 m, I.1970, Onraedt 70 M0354 ( BR); Andasibe-Mantadia Nat. Park, rocky ridge of Mt. Andrianavibe , 950-1050 m, X.1994, Pócs 9487/BQ ( EGR, GOET) .

DISTRIBUTION AND HABITAT. — Only known from Madagascar, where it grows on moist rock, rotten wood and bark in primary subhumid mid-elevation forest and heath forest, 850-1400 m.

DESCRIPTION

Plants c. 1.5-2mm wide and to 4cm long, unbranched or sparsely branched, branches intercalary, normal-leaved or flagelliform. Creeping rhizome-like stem present. Dorsal surface of stem with scattered paraphyllia along the dorsal midline, between the dorsal leaf bases. Stem leaves imbricate, falcato-secund when dry, obliquely to widely spreading when moist, ampliate, ovate to narrowly ovate-triangular, 1-2× longer than wide, often fragmenting, margins entire to toothed by few shortly linear to narrowly triangular teeth (1-3 cells long) made up of rather short cells, apex with 0-5 short teeth, ventral margin with 0-10 teeth, dorsal margin entire or with 1-7 teeth at the base (like in P. barteri ); dorsal bases shortly to moderately decurrent, strongly swollen, mostly covering the stem, ventral bases shortly and narrowly decurrent.Leaf cells irregularly subisodiametrical, 20-30µm wide in midleaf, with triangular to trabeculate trigones, leaf base with a very short (rudimentary) vitta-like area of larger cells, cells in the dorsal leaf base not elongate; cuticle smooth; oil bodies not observed. Underleaves absent. Gynoecia usually with two innovations, bracts larger than leaves,upright, strongly fragmenting, broadly ovate-triangular, c. 2.5-3 × 1.5-2 mm, toothed all along the margin, with numerous short teeth. Perianth ovate-oblong in outline, c. 2 mm long, not extending beyond the bracts, swollen, the mouth with numerous short, c. 2-3 cells long cilia and lacinia, perianth base not stalked. Vegetative reproduction by leaf fragmentation.

NOTES

Plagiochila sikorae (sect. Africanae) is a delicate, 1-2 mm wide species with long, sparsely branched stems (branching purely intercalary) and with small paraphyllia on the dorsal stem surface, between the leaf bases. The leaves are ovate to ovate-triangular, ± fragmenting and falcato-secund to widely spreading, with ampliate ventral bases and margins with few small teeth, 1-5 at the apex, 0-10 on the ventral margin and 0-7 on the dorsal base; the dorsal leaf bases are conspicuously decurrent, strongly swollen, usually toothed and are covering much of the stem surface, while the ventral bases are shortly decurrent. The leaf cells are almost isodiametrical, with triangular to trabeculate trigones, and are not elongate towards the base. The species is close to P. barteri and was treated as a synonym of the latter species by Vanden Berghen (1981); both species share toothed dorsal leaf bases. However, P. barteri lacks dorsal stem paraphyllia and is a more robust plant (to 5 mm wide), the leaves are more strongly toothed, with 20-50 teeth, and not falcato-secund when dry.