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 fracta Pócs ( Fig. 7 ) Plagiochila fracta Pócs, Phytotaxa 195 (2): 183 (2015) . — Type : Madagascar . Prov. Antsiranana , Manongarivo-Ambahatra Reserve, on ridge between the two branches of Mt. Ambahatra, c . 800 m , on rock in montane forest, 1250-1300 m , III.1999 , Geissler19691/1 ( holo- , G00281722; iso- , EGR; fide Pócs 2015 ). DISTRIBUTION AND HABITAT . — Only known from the type from Madagascar . DESCRIPTION (after Pócs 2015 ) Plants very small, 0.8-1.3 mm wide, to 1 cm long, very flaccid, irregularly branched, branches intercalary, rhizome-like creeping shoot present. Mature stem leaves contiguous, rather widely and horizontally spreading, sligthly asymmetrically oblong-ligulate, c . 2-3× longer than wide, widest in the middle, very fragile, irregularly fragmenting in the upper half, base not ampliate and not shouldered, apex rounded or 2-4 lobulate, without teeth; leaf bases shortly and narrowly decurrent. Leaf cells somewhat elongate, c . 15-2 µm wide in midleaf, with small trigones; leaf base without vitta-like area; cuticle smooth; oil bodies probably granular. Underleaves minute. Androecia slender, terminal to intercalary, with 3-5 pairs of bracts. Perianth campanulate, without stalk, perianth mounth laciniate. Vegetative reproduction by leaf fragmentation. A B C E D F FIG . 7. ― Plagiochila fracta Pócs : A , habit in dorsal view; B , habit in ventral view; C , detail of habit in ventral view; D , leaves; E , midleaf cells; F , basal leaf cells. Adapted from Pócs (2015) . Scale bars: A, B, 1 mm; C, D, 0.5 mm; E, F, 0.05 mm. NOTES Plagiochila fracta (sect. Heteromallae Lindenb.) is recognized by the very small plants with intercalary branching and horizontally spreading, oblong-ligulate, entire or shallowly 2-4 lobed leaves that are strongly fragmenting in the upper half ( Pócs 2015 ). The species may be related to P. pectinata , but the latter is a larger plant with ventrad, toothed leaves that are caducous, not fragmenting.