A review of the genus Macromitrium Brid. (Orthotrichaceae, Bryophyta) in New Caledonia Author Thouvenot, Louis Saint Léon, 66000 Perpignan (France) thouvenot. louis @ orange. fr louis@orange.fr text Cryptogamie, Bryologie 2019 2019-10-16 20 16 167 217 http://dx.doi.org/10.5252/cryptogamie-bryologie2019v40a16 journal article 10.5252/cryptogamie-bryologie2019v40a16 1776-0992 12215595 Macromitrium microstomum (Hook. & Grev.) ( Fig. 1A ) In Schwägr. Species Muscorum Frondosorum , suppl. 2, 2: 130 (1827). M. pacificum Besch., Annales de Sciences naturelles, Botanique , sér. 5, 18: 209 (1873) . — Type: New Caledonia , “in summo monte Mi”, Balansa 917 ,” in monte Humboldt”, Balansa 2536 ;” in monte Mou”, Balansa 2974 ( lecto- , Balansa 917 BM000982740 [ Vitt & Ramsay, 1985a ]; isosyn- , PC[PC0096533, PC0137855]!). M. pacificum var. brevisetum Thér. , Bulletin de l’Académie internationale de Géographie botanique 20: 99 (1910). — Type: New Caledonia , Mt Koghis, Franc s.n. ( lecto- , PC[PC0096531]!; isolecto- , PC[PC0137852-3]!). M. pacificum var. longisetum Thér. , Bulletin de l’Académie internationale de Géographie botanique 20: 99 (1910). — Type: New Caledonia , “Dent de St Vincent”, Franc s.n. ( lecto- , designated here PC[PC0096529]!) syn. nov . ILLUSTRATIONS AND DESCRIPTION . — Vitt (1983) ; Vitt et al. (1995) . DISTRIBUTION IN NEW CALEDONIA . — M. microstomum is frequent in North and South Provinces. TOTAL RANGE . — Australia . New Zealand , Indonesia , Philippine Islands , Papua New Guinea , South Pacific Islands, Hawaï, Central America, West Indies ( Vitt & Ramsay 2006 ). SELECTED SPECIMENS . — New Caledonia . Province Nord, Touho, Tipiléi valley, waterfall, 315 m , 12.X.2012 , Thouvenot NC1279 ; Ponérihouen, Aoupinié, 1000 m , 20.X.2012 , Thouvenot NC882 ; Hienghène, Panié massif, 1245 m , 9.X.2012 , Thouvenot NC1382 ; Ouégoa, Mandjélia, 730 m , 5.X.2012 , Thouvenot NC876 ; Province sud , Païta, Mt Humboldt, 1600 m , 31.VIII.2003 , F. Muller NC766 (DR); path to Mt Ouin, 900 m , 19.IX.2016 , Thouvenot NC2318 (PC); Dzumac massif, 840 m , 26.IX.2012 , Thouvenot NC881 ; Mt Mou, 900 m , 10.IX.2001 , F. Müller NC427 (DR); Sarraméa, Dogny plateau, 943 m , 26.IX.2016 , Thouvenot NC2267 (PC); Bouloupari, Mt Do, 875 m , 25.X.2012 , Thouvenot NC1023 (PC); Thio, Mt Ningua, 1284 m , elfin forest, 24.IX.2016 , Thouvenot NC2346 (PC); Yaté, Rivière Bleue Nature Park, 680 m , 20.IX.2016 , Thouvenot NC2326 ; Pic du Grand Kaori, 400 m , 4.X.2016 , Thouvenot NC2227 ; Dumbéa, Montagne des Sources Strict Nature Reserve, 745 m , 21.IX.2016 , Thouvenot NC2387 ; path to Mt Bouo, 850 m , 9.IX.2001 , F. Müller NC230 (DR). DESCRIPTION The types of Macromitrium pacificum as well as other New Caledonian specimens of M. microstomum are easily recognized with the naked eyes or with hand lens by the habit of the branches in dry condition together with the length of the setae.This species is characterized by: 1) dense branching, short and thin branches 2-4(-10) mm long, 0.5-1 mm wide, when dry regularly funiculate with leaves twisted together in rows spirally coiled around the branches, leaf apices incurved to circinate; 2) small leaves narrowly lanceolate (0.7-) 1-1.5 mm long; 3) cells smooth thorough, not bulging, thick walled, the upper ones small 5-10 µm long, 3-8 µm wide, the lower linear, up to 50 µm long, with narrow straight lumina; 4) perichaetia conspicuous, erect along the seta bases; 5) usually long thin setae (5-) 10-30 mm long; 6) capsules oblong, 1.5 mm long, with very small mouths and plicate erect rims, peristome single; 7) naked calyptrae; and 8) autoicous condition and spores isomorphic. In New Caledonia , M. microstomum can only be confused with M. taoense (see under this species). The varieties described by Thériot are distinguished only by the length of the setae which is known to be a variable feature in the Macromitrium species with medium sized setae. Therefore, we do not keep them as distinct species. ( Yu et al. , 2018 ). The synonymy of Macromitrium pacificum with M. microstomum has been highlighted by Vitt (1983) . Thereafter, Yu et al. (2018) have synonymized the variety brevisetum but hesitated to include the variety longisetum as they could not observe type specimen. Here we formalize its status and designate an original specimen as a lectotype . In New Caledonia , Macromitrium microstomum is a mountain epiphyte, very frequent above 600 m up to the highest altitudes, rare below ( 300-400 m ). It grows on trunks, branches and twigs in wet forests, riversides, elfin forests and mountain shrublands. It can be found in very shady environment, like near waterfall, as well as in sunny places in ultramafic bush.