Species of Oudemansiella are distributed worldwide mainly in tropical to south temperate zones. Morphological identification of the species is usually complex and may even be ambiguous, especially for O. canarii and O. cubensis, since they share many similar characters. They have been considered synonyms by several authors. There are no recent descriptions or detailed illustrations of Oudemansiella species from Argentina, and molecular data are practically null. In this work these species were described and illustrated making use of new collections, culture data, and nrITS phylogenetic analysis. It was not possible on the basis of the results to differentiate the species macroscopically, but these were differentiated at the microscopic level, mainly by their pileipellis structure. Phylogenetic analysis from nrITS sequences enabled the molecular identification of these two species, and the cultivation of basidiomes on lignocellulosic substrate allowed us to affirm that both species have a hemiangiocarpic development.

Five new combinations in Myriopus (Heliotropiaceae) are proposed in this paper: Myriopus andrade-limae, M. isabellinus, M. mapirensis, M. selleanus, and M. subsessilis. Myriopus isabellinus and M. selleanus are restricted to Costa Rica and Haiti, respectively, and other three species are distributed in South America; M. andrade-limae is endemic to Brazil.

Two additions are proposed for the Solomon Islands orchid flora. Dendrobium biflorum is a new record, while D. stella-portus is proposed as a new species.

Continuing studies of Malesian Orchidaceae find that it is necessary to subsume Platystyliparis into Alatiliparis requiring nine combinations, propose a small flowered but showy new Dendrobium, expand the circumscription of Oberonioides, requiring five combinations, move Calanthe subhamata to Styloglossum, and propose a new Tropidia.

We provide a general introduction to the prodromi to Flora Costaricensis, and an introduction to the precursors of subtribe Pleurothallidinae. We present a systematic revision of the genus Echinosepala for the flora of Costa Rica and a detailed discussion of molecular evidence with regard to most Costa Rican taxa, aimed at phylogenetically framing Echinosepala within the subtribe Pleurothallidinae, recognizing internal relationships among the species in the genus, and proposing evolutionary hypotheses. We recognize 10 species of Echinosepala in Costa Rica. Each species is described and illustrated with one or more botanical drawings and photographs, all based on Costa Rican material. Etymology, distribution, ecology, distinguishing features, and affinities with other taxa in the genus are discussed, taxonomic notes are provided, and a list of selected material examined for this study is included for each taxon. Two new species of Echinosepala, E. glenioides and E. isthmica, are described and illustrated, and their relationships are discussed. New combinations are proposed in Echinosepala for Pleurothallis alexandrae and P. pastacensis, and the former species is neotypified.

Calliandra subspicata (Fabaceae) hitherto had been reported from Pernambuco and Bahia, states of the Northeast Region of Brazil. Here we report this species from Paraíba state, the third state of this region. It was observed and collected at the Pico do Jabre State Park, a conservation unit situated at the residual massif of the Depression Sertaneja on the Borborema Plateau, which reaches an altitude of 1197 m. The identification was made on the basis of current literature. A morphological description, images, information about the area where the taxon was collected, and a key for identification of the species of Calliandra recorded in Paraíba state are provided.

Bacopa llanorum, a new species from the seasonally flooded savannas of the “Llanos” region of Colombia (Arauca department) is described and illustrated, and its morphological relationships are discussed. On the basis of its dimorphic leaves (the innermost blade filiform, uppermost lanceolate-ovate), the new species does not appear to be allied to any other Bacopa species. However, it shares several other features with B. reptans. A new combination, Bacopa debilis, is proposed to replace Caconapea debilis. In addition, ecological information of the genus in “Los Llanos” of Colombia and Venezuela, and ecological and floristic notes about the eolic-limose plains, are included. A key for identifying species of Bacopa in this region is also provided. Bacopa llanorum is remarkable for its foliar dimorphism, in an otherwise predominantly homomorphic-leaved genus, and it increases to 20 the number of species of the genus in the “Llanos del Orinoco” bioregion.

Besleria naquenensis is described and illustrated on the basis of a collection from the understory of seasonally flooded forests drained by black waters located in the lower “Río (Caño) Naquén,” northwestern base of “Serranía de Naquén,” upper Guainía River basin, Guainía Department, Colombia, and its relationships with related species are discussed. This new species shares features with three species (B. gibbosa, B. neblinae, and B. yatuana) of section Neobesleria subsection Axillares. Morphologically, it is closest to B. yatuana, but it differs in its leaves, inflorescences, calyx, and corolla. In addition, habitat information, a distribution map, and data of its conservation status are included. An identification key of 27 species of Besleria found in the Rio Negro basin (Brazil, Colombia, and Venezuela) and adjacent regions is also provided. This new species elevates to 66 the number of Besleria taxa for the flora of Colombia, the country with the highest diversity of the genus.

Lepanthes is one of the most species-rich genera of orchids in the Neotropics, with most of the species found in medium to high elevation forests and few species in lowlands. We describe and illustrate Lepanthes osaensis, a new species from the very wet lowland forest of Península de Osa, Costa Rica. It is similar to Lepanthes cuspidata but differs mostly in the vinous leaves; smaller sepals; the narrower, bilobed petals; and the smaller lip with triangular blades. Notes on its distribution, habitat, flowering, and conservation status, as well as discussion of a taxon with similar morphology, are provided.

Two new species of Podandrogyne, P. flammea, endemic to Pacific coastal and western Andean Ecuador and Colombia, and P. websteri, restricted to four northern provinces of Ecuador but found mostly in Pichincha, are described and illustrated. These taxa are generally distinguished by flower and fruit size and leaf blade number and texture. A general likeness suggests affinity to the species cluster represented by P. glabra.

On the basis of previously documented genetic evidence, which correlates with morphological traits and a well-defined biogeographic pattern of distribution, Hilairanthus Tiegh. is recognized and reinstated as a genus of mangrove segregated from Avicennia (Acanthaceae). The genus is lectotypified, and the following combinations are formally proposed for Hilairanthus germinans, H. bicolor, and H. schaueriana.

Calyptranthes magna, a new species of Myrtaceae from Yasuní National Park (Orellana, Ecuador), is described and illustrated.

The transfer of Turnera acangatinga and T. ibateguara to the genus Oxossia, as synonyms of the names O. annularis and O. pernambucensis (Turneraceae, Passifloraceae s. l.), respectively, is proposed herein.

Professor Yan-Cheng Tang, also known as Yen-Cheng Tang, (汤彦承, given name Yan-Cheng, surname Tang; abbreviated Y. C. Tang), passed away on August 6, 2016, in Beijing at the age of 90. He was a highly respected plant taxonomist for his massive contributions to plant taxonomy in China and for the number of botanists he influenced. A brief biography and a summary of his importance in the development of plant taxonomy in China during the latter half of the 20th century is presented.