Novitates Gabonenses 93: a fresh look at Podostemaceae in Gabon following recent inventories, with a new combination for Ledermanniella nicolasii Author Bidault, Ehoarn https://orcid.org/0000-0001-5029-8069 Missouri Botanical Garden, Africa & Madagascar Department, St. Louis, Missouri, USA & Institut de Systematique, Evolution, et Biodiversite (ISYEB), Unite Mixte de Recherche 7205, Centre National de la Recherche Scientifique / Museum National d'Histoire Naturelle / Ecole Pratique des Hautes Etudes, Universite Pierre et Marie Curie, Sorbonne Universites, Paris, France ehoarn.bidault@mobot.org Author Boupoya, Archange https://orcid.org/0000-0002-8926-8737 Institut de Recherche en Ecologie Tropicale (IRET), Libreville, Gabon & Herbier National du Gabon, Libreville, Gabon Author Ikabanga, Davy U. Laboratoire d'Ecophysiologie et de Biodiversite Vegetale, Departement de Biologie, Faculte des Sciences, Universite des Sciences et Techniques de Masuku (USTM), Franceville, Gabon Author Nguimbit, Igor Laboratoire d'Ecophysiologie et de Biodiversite Vegetale, Departement de Biologie, Faculte des Sciences, Universite des Sciences et Techniques de Masuku (USTM), Franceville, Gabon Author Texier, Nicolas https://orcid.org/0000-0002-4045-992X Missouri Botanical Garden, Africa & Madagascar Department, St. Louis, Missouri, USA & Evolutionary Biology and Ecology Unit, Faculte des Sciences, Universite Libre de Bruxelles, Brussels, Belgium Author Rutishauser, Rolf Herbarium et Bibliotheque de Botanique africaine, Universite Libre de Bruxelles, Brussels, Belgium Author Mesterhazy, Attila https://orcid.org/0000-0001-7952-5990 Department of Systematic and Evolutionary Botany, University of Zurich, Switzerland Author Stevart, Tariq https://orcid.org/0000-0002-6212-0361 Missouri Botanical Garden, Africa & Madagascar Department, St. Louis, Missouri, USA & Evolutionary Biology and Ecology Unit, Faculte des Sciences, Universite Libre de Bruxelles, Brussels, Belgium & Centre for Ecological Research, Wetland Ecology Research Group, Debrecen, Hungary text Plant Ecology and Evolution 2023 2023-03-01 156 1 59 84 http://dx.doi.org/10.5091/plecevo.96359 journal article http://dx.doi.org/10.5091/plecevo.96359 2032-3921-1-59 A3301095CCAD56078E5F4CA25FE7E738 Ledermanniella pygmaea (Pellegr.) C.Cusset (Cusset 1984: 266) Figs 6H , 7B Sphaerothylax pygmaea Pellegr. ( Pellegrin 1927a : 268) Type . GABON • Samba waterfall in the Ngounie river, near Sindara ["Chutes de Samba, Sindara, dans la Ngounye" ]; 30 Jun. 1917 ; [ 1°02 '23" S , 10°41 '44" E ]; 35 m ; fl., fr.; Le Testu 2202 ; holotype : P [P00179351]; isotype: BM [BM000910392] . Distribution. Endemic to the Ngounie and Louetsi rivers, in Gabon. Before 2017, this species was solely known from the type collection made at Samba (or Tsamba) falls on the Ngounie river, west of Sindara ( Le Testu 2202 , gathered in 1917). It was found again one century later, in 2018, at three different sites on the Louetsi river, a tributary of the Ngounie , and collected 10 times in 2018 and 2021. Surprisingly, recent inventory at the type locality did not allow to collect this species again, despite the apparent lack of disturbance and immediate threat to this site. Habitat and ecology. Falls in rivers from ca 35 to 170 m wide, 35-450 m in elevation. It is very localized when encountered, but forming dense, apparently monospecific mats. Flowers and fruits were collected in June and August. In the Louetsi river, it has been found in close vicinity with L. aloides and L. pusilla . This species seems restricted to falls, in fast flowing water, as it was not collected in smaller rapids areas in the Louetsi river. Notes. The presence of both stemless shoots and developed stem up to 8 mm long was already mentioned by Cusset (1984) , and is confirmed by the recent observations. This species is recognizable by the combination of ribbon-like root, pollen in dyads, a single stamen, leaves arranged all around the stem (not distichous), that are linear, entire to 3-4 times forked. When a developed stem is present, the leaves at base are usually shorter, sometimes damaged, which can give the impression of stem-scales. Nevertheless, there is a continuum in length and shape between basal and apical leaves, which suggests no true stem-scales (as typical for Inversodicraea ) are present in this species.