The genus Plagiochila (Dumort.) Dumort. (Marchantiophyta) in Madagascar Author Gradstein, S. Robbert Meise Botanic Garden, 1060 Meise (Belgium) and Institut de Systématique, Évolution, Biodiversité (UMR 7205) Sorbonne Université (MNHN, EPHE, CNRS), Muséum national d’Histoire naturelle 57 rue Cuvier, case postale 39, 75005 Paris (France) robbert. gradstein @ mnhn. fr (corresponding author) gradstein@mnhn.fr Author Reeb, Catherine Institut de Systématique, Évolution, Biodiversité (UMR 7205) Sorbonne Université (MNHN, EPHE, CNRS), Muséum national d’Histoire naturelle 57 rue Cuvier, case postale 39, 75005 Paris (France) catherine. reeb @ mnhn. fr reeb@mnhn.fr text Cryptogamie, Bryologie 2022 2022-05-16 20 5 65 106 http://dx.doi.org/10.5252/cryptogamie-bryologie2022v43a5 journal article 10.5252/cryptogamie-bryologie2022v43a5 1776-0992 12215006 Plagiochila vandenberghenii Gradst. , sp. nov. ( Fig. 23 ) Plagiochila vandenberghenii Gradst. , sp. nov. (sect. Vagae ) stands out by irregularly pinnate to dichotomous branching by terminal and intercalary branches, and somewhat distant, horizontally spreading, narrowly oblong-rectangular, non-ampliate leaves ( c . 2.5-3× longer than wide) with the apex bifid by two large, lobe-like teeth, and a slightly bordered leaf margin with more elongate cells in 1-2 rows; 2-5 additional, smaller teeth are produced at the leaf apex and on the distal half of the ventral and dorsal margin. Underleaves are absent. HOLOTYPE . — Madagascar . Prov. Fianarantsoa • Ranomafana Nat. Park , opposite park gate, near Ambodiamontana settlement, Namorona river valley, on bark in partially degraded lower montane rainforest, 865-1015 m , VII.2004 , Pócs et al. 04118/AY ( holo- , EGR !; iso- , GOET !). ADDITIONAL SPECIMEN EXAMINED . — Madagascar . Prov. Fianarantsoa • Ranomafana Nat. Park, near park gate, 1067 m , on twigs, Reeb CR 17 M 610 ( PC ). ETYMOLOGY . — Named after the late Professor Constant Vanden Berghen, renowned Belgian botanist and bryologist who has laid the basis for our knowledge of Plagiochila in Madagascar . DISTRIBUTION AND HABITAT . — Only known from Ranomafana National Park (two collections) on Madagascar , growing on bark. DESCRIPTION Plants 3-4 mm wide, to 4 cm long, irregularly branched below and on broken shoots by intercalary branches, dichotomous above by terminal branches, rhizome-like creeping shoot present. Mature stem leaves distant to contiguous, widely and horizontally spreading (not ventrad), narrowly and subsymmetrically oblong-rectangular, 2.5-3× longer than wide, on branches up to 4× longer than wide, not caducous, not ampliate and not shouldered, margins almost parallel, unbordered or weakly bordered, with 5-8 teeth in the upper half made up of rectangular cells; leaf apex bifid by two long, lobe-like teeth, to 10-15 cells long, the two teeth separated by a wide rounded sinus, sometimes one of the two teeth is broken, a smaller tooth may be present in the sinus between the two large lobe-like teeth and occasionally the apex is trifid, tip cell of the teeth not much longer than the rest of the cells, distal portion of ventral and dorsal leaf margin with 1-3 smaller teeth, lower half of the margins and bases entire; leaf bases shortly and narrowly decurrent, the decurrent ventral part maximally 0.15 mm long. Leaf cells subisodiametrical to slightly elongate, 1-1.5× longer than wide, 18-30 µm wide in midleaf, trigones small but not swollen, triangular with concave walls and frequently radiate along the longer walls, cells along the margin sometimes more elongate and with a thicker inner tangential wall, forming a weak border, leaf base without vitta-like area, cuticle smooth; oil bodies not observed. Underleaves absent. Androecia not seen. Perianth campanulate, slightly elevated above the bracts on a short, thickened stalk. Vegetative reproduction not seen. NOTES Plagiochila vandenberghenii Gradst. , sp. nov. (sect. Vagae ) is readily distinguished from all other African members of the genus Plagiochila by the horizontally spreading, narrowly oblong-rectangular, non-ampliate leaves ( c . 2.5-3× longer than wide) with a strongly bifid apex, with two long teeth. In its horizontally spreading, bifid leaves, the new species cannot be confused with any other African species of Plagiochila and only resembles the Asian P. bicornuta Steph. (synonym: P. laxissima Schiffn. ; fide So 2001 ), but the apical teeth in latter species are smaller and terminal branching is lacking. B C A D G E F H I J K L M FIG . 23. ― Plagiochila vandenberghenii Gradst. , sp. nov. : A , shoots; B , shoot in dorsal view with terminal branching; C , intercalary branching; D , shoot in ventral view; E , stem leaves; F , branch leaves; G , branch in dorsal view; H , I , leaf margin cells; J , leaf base; K , leaf apex; L , shoot with perianth, two leaves at perianth base removed to show the perianth stalk; M , female bracts. From Reeb CR17M610 (PC). Scale bars: A, 5 mm; B-G, J, K, 1 mm; H, I, L, 0.1 mm; M, 0.025 mm. The perianths in the new species are campanulate.According to Heinrichs (2002) , campanulate perianths are characteristic of unfertilized gynoecia, but the perianths in P. vandenberghenii Gradst. , sp. nov. had mature sporophytes.