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Floristic taxonomic research, looking for constant differences between species, is a very time-consuming and slow process. The flora of the Malay Archipelago is estimated to have 45,000 vascular plant species and the Flora Malesiana project that describes them has completed c. 1/3rd in 75 years. Presently, the flora is heavily threatened because of land use and climate change. We have to speed up the flora writing to understand what will be threatened and how to counter the threats. Innovation using Next Generation Sequencing of DNA to find the species in combination with Image Recognition might help to increase speed. Another aspect is cooperation, more international scientists should be involved, also students and citizens via citizen science projects. Citizens can help to gather information (observations and collecting). Once the flora is better known, monitoring of the flora by regular inventories (done by non-scientists in the Netherlands) helps to see which plants are threatened or become plagues and causes can then be investigated. Monitoring will help to change energy consumption (no more fossil energy), agriculture, industry, and living: improve our climate, and save the planet.

A revision of Leptopus and Notoleptopus (Phyllanthaceae tribe Poranthereae) in Malesia is presented. Both genera are present with a single species in Malesia, L. australis and N. decasnei, respectively. Phylogenetically the two genera are distinct, but morphologically their differences are minimal. Nomenclature, descriptions, distributions and various notes are presented, just as a technical drawing of both species.

Dalechampia is a mainly South American genus of generally climbing shrubs with usually sharp stiff trichomes in some of the inflorescence parts. The bisexual inflorescences are very condensed and subtended by two, often showy, large bracts. The three pistillate flowers are separate from the staminate subinflorescence (both groups with their own bracts). The staminate subinflorescence contains groups of staminodial-like bractlets that provide resin for female bees or fragrance for male bees. In west Malesia (Sumatra and Java) one indigenous species is found, the climbing D. bidentata, and occasionally cultivars of the subshrub D. spathulata.

Three new species of Breynia are described for Malesia, B. longistyla from Borneo, B. papillosa from New Guinea, and B. suborbicularis from Sulawesi. They are primarily distinguished by characters of indumentum, leaves, and styles. Ten lectotypes and one neotype are designated, and one new synonym is proposed.

Within the morphologically diverse pantropical genus Phyllanthus, many subgenera, sections and subsections are recognized. While most taxonomic revisions often focus on local floras, closely related and often resembling species are not always treated in full. Subgenus Macraea is here revised for the first time over its whole distribution, including an identification key and descriptions of its species with distributions, ecology, uses and vernacular names. The currently acknowledged varieties of Phyllanthus distichus are rejected due to inadequate morphological differences. Phyllanthus panayensis is synonymized with P. lancifolius. Phyllanthus alpestris has now become a variety of P. glaucophyllus because of the resemblance in morphology and distribution. The species complex around Phyllanthus virgatus remains taxonomically difficult, but Phyllanthus virgatus var. gardnerianus and Phyllanthus virgatus var. hirtellus are here recognized on the species level as P. gardnerianus, stat nov. and P. tararae, stat & nom. nov. A new species from the Philippines, Phyllanthus ridsdalei, is described

A deciduous shrub previously included in Ficus talbotii for many years, is now regarded as a new species, Ficus pongumphaii. It is morphologically distinct from F. talbotii with as typical characters the densely brown pubescent to tomentose or villous on leafy twig; the elliptic, suborbicular to obovate leaf blades that are brown tomentellous on the upper surface and brown floccose tomentose to villous underneath; the pedunculate figs are obovate, brown floccose or villous outside and have internal hairs. The leaf anatomy shows a multiple epidermis on both surfaces; enlarged lithocysts on both sides of the lamina, which are more abundant adaxially and with very few abaxially. The species, endemic to Thailand, is named after the great Thai dendrologist, Associate Professor Somnuek Pongumphai.

Trigonostemon is taxonomically revised for Malesia based on herbarium collections and field observations. Thirty-eight species are recognized in Malesia, of which four of uncertain status and four newly described. The previous infrageneric classifications are briefly reviewed, but none is accepted. Some useful characters are discussed. An identification key, nomenclature, descriptions, typification, geographic distributions and taxonomic notes are provided.

The genus Baliospermum is revised for the Malesian area. A single, variable species is recognized: B. solanifolium.

The genus Cnidoscolus, a species rich genus in the Americas, has been introduced in the Philippines. A cultivar of Cnidoscolus aconitifolius is used as vegetable and has been collected from gardens in Manila and Pasay City and two times near Cebu City. It cannot be excluded that it has escaped cultivation there, but the species does not appear to be invasive.

Breynia subgenus Hemisauropus is reduced to Breynia section Cryptogynium. Arguments are given to regard the Breynia quadrangularis complex as a single species.

The genus Actephila (Phyllanthaceae) is distributed from India in the north-west to Thailand and via Malesia to the Melanesian Islands and Australia in the south-east. Eleven species are recognized of which three are newly described, A. discoidea with long leaf apices and a fleshy nectar discs, A. emarginata with an emarginate leaf base, and A. stipularis with large stipules. Further, A. javanica is synonymized with A. excelsa; and a former synonym or separate variety, A. excelsa var. acuminata, is recognized as distinct species, but had to be synonymized under A. subsessilis. Actephila puberula, not present in Malesia, but often synonymized with A. excelsa, is kept separate because of the hairy ovary and different base of the leaf blades.

Jatropha, a widespread, species rich genus, ranges from the Americas and Caribbean to Africa and India. In Malesia five species occur, all of which were introduced and originated in Central and South America. The five species are revised and an identification key, nomenclature, descriptions, distributions, ecology, vernacular names, uses and notes are provided. Special attention is given to the uses of J. curcas, because it is steadily gaining popularity as a potential biofuel plant and, because of that, is being cultivated more often.

The genera Bischofia and Hymenocardia both have a single species in Malesia. The two genera were always difficult to classify, both once formed their own family, but are now firmly embedded in the Phyllanthaceae. Of both genera a more complete nomenclature and biogeography is presented.

The genus Blumeodendron (Euphorbiaceae) comprises nine species and is distributed from the Andaman Islands and Myanmar in the west through Malesia to the Bismarck Archipelago in the east. Two species are newly described, B. gesinus, with ridged fruits, and B. endocarpum, with a thickened endocarp around each seed. Three former synonyms, B. novoguineense (new name for Bennettia papuanum), B. philippinense and B. subrotundifolium, are reinstated as species. Two important characters were newly discovered, the presence of small lepidote hairs in all species and the indehiscent fruit of B. endocarpum

The variability of Ostodes paniculata var. paniculata, the only representative of the genus in Malesia, is described. The variety and the species have a disjunct distribution as they are found in India to Southern China and the Southeast Asian mainland, Sumatra and Java. The variability in leaf glands, domatia, sepals, and seeds shows geoclines. Depending on one’s view the genus has two more varieties or species, both more hairy and occurring from N Thailand to China or in China only. Their nomenclature is provided, as is the nomenclature of the many excluded species, once part of a larger generic concept of Ostodes, but now mainly part of Dimorphocalyx and Paracroton. Typical for Ostodes are the red latex, the ovate, rather large serrate leaf blades with basally two raised glands, the paniculate inflorescences with relatively large flowers with petals and many (nearly) free stamens, and the large woody fruits.

Dimorphocalyx, a small genus ranging from Sri Lanka to Indomalesia to Australia, has eight species in Malesia, of which one is here raised from variety to species level and another, endemic in the N Moluccas, is newly described. Dimorphocalyx murinus and – tentatively – D. loheri are synonymised with D. denticulatus, and D. luzoniensis is synonymised with D. malayanus. Dimorphocalyx cumingii is regarded as a species of Trigonostemon. The differences between Dimorphocalyx, Ostodes, Paracroton (formerly Fahrenheitia), and Trigonostemon are discussed.

Malesia harbours one, possibly two species of Blachia. In the Philippines B. philippinensis is found and this species is not synonymous with B. andamanica. In literature B. andamanica has been recorded for west Malesia, but no specimens were seen. Based on its presence in Peninsular Thailand and the Andamans it is likely to be present in Peninsular Malaysia. The most distinct difference between both species is in the indumentum of the ovary, sparsely hairy in the lower half versus densely and completely sericeous, respectively.

Derris solorioides is described as a new species and illustrated. This species is only the second calciphilous and true-paniculate species of Derris ever recorded. The species was found in isolated and protected limestone areas surrounded by agricultural areas in Nakhon Sawan province, North-Central Thailand. It is characterized by its rather smaller flowers but with more ovules than other species of Derris, and 1-winged pods showing a dark-coloured pericarp around the seeds without thickening of the pericarp. The characters of the pods are similar to those found in Solori, a genus once synonymized with Derris and, therefore, the epithet ‘solorioides’ was assigned. This species appeared to be a distinct taxon in the molecular phylogeny, separate from its morphologically highly similar species, D. marginata. It is also a member of a lineage of Derris consisting of species with a deviating type of inflorescence: intermediate forms and true panicles, which is quite uncommon in this genus. The relationship with its closely related species is discussed, and a key to the species of Derris in the ‘deviating type of inflorescence’ clade is presented.

A small fig tree has been misidentified as Ficus orthoneura for a long time. However, morphologically it is distinct from F. orthoneura and F. hookeriana. Typical are the ellipsoid, puberulous receptacle and caducous basal bracts. Leaf anatomy shows a multiple epidermis with the cells in the inner layer much larger than in the outer layer and thus both layers resemble an epidermis with a separate hypodermis. The abaxial cuticle is strongly sculptured, the palisade layer shows some long subdivided cells, and enlarged lithocysts are only present abaxially. Because of these differences we hereby describe it as a new species, named in honour of Cornelis (Cees) Berg: Ficus cornelisiana.

Previous molecular phylogenetic studies indicated expansion of Breynia with inclusion of Sauropus s.str. (excluding Synostemon). The present study adds qualitative and quantitative morphological characters to molecular data to find more resolution and/or higher support for the subgroups within Breynia s.lat. However, the results show that combined molecular and morphological characters provide limited synergy. Morphology confirms and makes the infrageneric groups recognisable within Breynia s.lat. The status of the Sauropus androgynus complex is discussed. Nomenclatural changes of Sauropus species to Breynia are formalised. The genus Synostemon is reinstated.

A small fig tree has been misidentified as Ficus orthoneura for a long time. However, morphologically it is distinct from F. orthoneura and F. hookeriana. Typical are the ellipsoid, puberulous receptacle and caducous basal bracts. Leaf anatomy shows a multiple epidermis with the cells in the inner layer much larger than in the outer layer and thus both layers resemble an epidermis with a separate hypodermis. The abaxial cuticle is strongly sculptured, the palisade layer shows some long subdivided cells, and enlarged lithocysts are only present abaxially. Because of these differences we hereby describe it as a new species, named in honour of Cornelis (Cees) Berg: Ficus cornelisiana.

The most recent phylogenetic analyses of the Malphigiales place the family Rafflesiaceae in the Euphorbiaceae, near the base of the clade. Combining both families is not an attractive option, because the Rafflesiaceae are very recognisable, while the Euphorbiaceae is one of the most polymorphic families around. The solution is to recognize the basal part of the Euphorbiaceae as Peraceae, which will leave the Rafflesiaceae and rest of the Euphorbiaceae untouched. The typical characters of the Peraceae are discussed. Within Malesia the family contains two genera, Chaetocarpus (1 species) and Trigonopleura (3 species). All species are mainly west Malesian taxa. They have as shared typical characters obovate stipules, united stamens and densely hairy fruits. The treament contains nomenclature, identification keys, descriptions, drawings, photos and notes on districution, ecology, uses, etc.

Dicoelia was always considered to be a monotypic genus. Typical are the hooded (cucullate) petals that form cavities in which juvenile thecae of adjacent stamens are protected. Specimens of Sumatra appear to represent a new species. The Sumatran specimens have stipules that fall slightly later and they show morphological differences in the pistillate petals, pistillode, columella and hilum. Newly described structures are disc glands (thought to be absent), probably not functional, but present in the flowers of both sexes and a gynophore in the pistillate flowers. Dicoelia is considered as a member of the Phyllanthaceae conforming with the latest molecular phylogenetic results; a classification that agrees with the presence of two ovules per locule.

Formerly, the Picrodendraceae formed the subfamily Oldfieldioideae within the Euphorbiaceae. The introduction discusses the taxonomy, wood and pollen morphology. Only four genera are present in Malesia. Three of them are either monotypic (Kariothamnus) or comprise only a single species (Choriceras and Petalostigma) in New Guinea. Austrobuxus (three species) is the only widespread genus in Malesia. The taxonomic treatment contains descriptions, keys, drawings and notes on distribution, ecology, etc.

Twenty-eight species of Acalypha are recognized in Malesia. Acalypha paniculata is the sole member of subgenus Linostachys in Malesia and the rest of the species belong to subgenus Acalypha. Four previously synonymized species are resurrected as distinct species, namely A. angatensis, A. cardiophylla var. cardiophylla, A. grandis, and A. wilkesiana. Four species names are newly reduced to synonymy. The molecular phylogenetic analyses indicate that Acalypha is monophyletic, as is the subgenus Acalypha. The early-diverging lineages in the genus, and its closest outgroup, consist of African species. The Malesian species do not form a monophyletic group although the molecular data strongly support two small clades within the region that are morphologically homogeneous. The classification system that Pax and Hoffmann applied to subgenus Acalypha, which is based primarily on inflorescence morphology, appears to be unsatisfactory and incongruent with the phylogenetic analyses.

An identification key to all Malesian species of Mallotus was still lacking. So far, only keys per section of Mallotus or keys per island were generated. This is the first attempt to create a key for all species of Mallotus in Malesia.

Distribution patterns or the recognition of phytogeographical areas is usually based on the presence and absence of species. The taxa on which the analyses are based remain virtually anonymous. Here we want to determine which Malesian plant families (within the sample) are responsible for species richness and composition patterns. The other aim is to determine whether the different islands groups in Southeast Asia can be grouped into separate phytogeographical areas. A Principal Coordinates Analysis (PCO) showed the presence of three phytogeographical areas within Malesia: The Sunda Shelf (Malay Peninsula, Sumatra, Borneo) in the west, the Sahul Shelf (New Guinea) in the east, and all remaining central areas forming Wallacea. The latter can be divided into two parts (Java and the Lesser Sunda Islands versus the Philippines, Sulawesi and the Moluccas). Only twenty plant families (out of 164 sampled) account for most of the biodiversity on the island groups, both in total and endemic species numbers. These twenty families show a limited number of species richness patterns that are significantly associated with one or several of the detected phytogeographical areas. Only a few plant families were equally common throughout the whole Malesian region. Conservation efforts in Malesia should take this spatial distribution pattern into account in order to maximise preservation of both species diversity and complementarity.

Two approaches to revise large genera are discussed. The first approach can be done by a single person, who revises the genus area after area. The other approach is by a team that revises per infrageneric taxon (preferably a single person per infrageneric group). The two approaches have their positive and negative sides, but both give good results. One problem with both approaches is to keep an overview of a possible infrageneric classification. The latter problem can be tackled by performing phylogenetic analyses based on molecular markers (providing core phylogeny) in combination with morphological, palynological, and anatomical data (providing apomorphies for infrageneric taxa).

A large amount of unidentified material of the Neotropical genus Guatteria (Annonaceae) is lying on herbarium shelves around the world. Here twelve species are described in an attempt to reduce this amount of unidentified material. Next to this, previously unidentified material is now assigned to G. asplundiana, G. microcarpa, G. pastazae, and G. scalarinervia, four previously described but poorly known species, thus providing a clearer circumscription of these species. Furthermore, G. discolor and G. megalophylla appear to have a wider distribution than previously thought. Lastly, G. macrantha, a curious species only known from the type, is excluded from the genus and referred to Uvaria. With the description of twelve new species and the synonymizing of one, the total number of species in Guatteria adds up to over 300, thus rivalling Inga (Fabaceae) and Ocotea (Lauraceae) for the status of largest genus of Neotropical trees.

The range of diagnostic morphological features in the whole genus Mallotus is reviewed as background to the taxonomic treatment of section Rottleropsis s.l. Special emphasis is given to the indumentum, habit, stipules, leaves, extrafloral nectaries, domatia, inflorescences, flowers, pollen and fruits. Notes on the geographical distribution, ecology, pollinators, fruit and seed dispersal, and uses of the genus are also presented. The section Axenfeldia is reduced to sect. Rottleropsis on account of the absence of suitable morphological characters to distinguish them. A taxonomic revision of 38 species of sect. Rottleropsis s.l. from Malesia, Thailand and Africa is presented, together with regional and synoptical identification keys, distribution maps and illustrations. Four new species are described: Mallotus connatus, M. longinervis, M. minimifructus and M. mirus. Several non-Malesian species not included in this revision are briefly discussed. This paper concludes a series of taxonomic revisions of the genus Mallotus in Malesia and Thailand.

A recent molecular phylogenetic study of Mallotus and related genera showed that three small Asiatic genera are clearly part of a strongly supported main Mallotus clade (Mallotus s.s. clade), rendering the genus paraphyletic. In this paper these genera, Neotrewia, Octospermum and Trewia, are merged with Mallotus. The monotypic Neotrewia and Octospermum were originally described within Mallotus and are now transferred back to it. Trewia was never included in Mallotus; it has two distinct species, for which new combinations within Mallotus are made. A full taxonomic treatment with descriptions, distribution maps and drawings is given for the species transferred, and a new generic description for Mallotus is provided. The morphology of the newly transferred species in comparison to Mallotus in general and to related species in particular is discussed.

Based on phylogenetic studies with DNA sequence data, the formerly monotypic genus Cordemoya was recently expanded with 16 additional species previously assigned to Mallotus. However, the earliest legitimate generic name available is Hancea, and, therefore, Cordemoya is here reduced to Hancea (20 new combinations are proposed). Subsequently, the subgenus and section Diplochlamys from Asia are renamed to Hancea. Additionally, the genus Adisca is lectotypified with Adisca floribundus (= Mallotus floribundus).

A recent phylogenetic study based on DNA sequence data detected a well-supported clade of a number of Mallotus species together with the genus Cordemoya. This clade is distinct from the large Mallotus s.s. clade. In this paper, Cordemoya (formerly monotypic with C. integrifolia from the Mascarene Islands) is expanded with sixteen additional species previously assigned to Mallotus. Taxa transferred to Cordemoya are: Mallotus sections Hancea and Oliganthae from Asia and M. baillonianus, M. capuronii, and M. spinulosus from Madagascar. The genus Cordemoya can be distinguished from Mallotus s.s. by the presence of pollen with areolate ornamentation with scabrae (perforate/microreticulate ornamentation with scabrae in the sample of Mallotus s.s. studied up to now) and of capitate glandular hairs with multicellular stalks and sessile peltate-stellate hairs with a central cell (spherical to disc-shaped multicellular glandular hairs in Mallotus). In the new circumscription of Cordemoya two subgenera are recognized: Cordemoya from Madagascar and Mascarenes and Diplochlamys from Asia. The latter is divided into two sections: Diplochlamys (former sect. Hancea), and Oliganthae. A taxonomic revision of part of these taxa is provided (excl. section Diplochlamys); descriptions, distribution maps, habit drawings and a key are included.

Mallotus kongkandae Welzen & Phattar. was thought to be endemic to Thailand, but it also occurs in China, though known under other names. The new list of synonyms, a distribution map, notes on habitat and ecology, and collector details are included.

Mallotus concinnus Airy Shaw, M. havilandii Airy Shaw, M. insularum (Airy Shaw) Slik, and M. miquelianus (Scheff.) Boerl. are very similar in appearance, with opposite leaves of which one large and elliptic, and the other reduced and more or less obcordate. However, a detailed look revealed enough differences to regard them as distinct species.

The Mallotus wrayi King ex Hook.f. complex on the Sunda Shelf of the Malay Archipelago (Malay Peninsula, Sumatra, Java, Borneo) appeared to comprise four species instead of a single, very heterogeneous one. Two synonyms (M. caudatus Merr. and M. lancifolius Hook.f.) are resurrected and a new species, M. spinifructus, is described. Important characters can be found in the density of the hairs (glandular scale-like, simple or stellate), type of stellately bundled hairs, lengths of inflorescences, bracts, and bracts of the terminal bud, and in the stigma width and hairiness.

A revision of the Malesian species in the genus Cleidion is presented. Cleidion javanicum is shown to be the correct name for the widespread type species (instead of the name C. spiciflorum). A new species, C. luziae, resembling C. javanicum, is described from the Moluccas, New Guinea and the Solomon Islands. In addition, C. salomonis is synonymised with C. papuanum and C. lanceolatum is treated as a variety of C. ramosii. In total 7 Malesian Cleidion species are recognized. Cleidion megistophyllum from the Philippines cannot reliably be confirmed to belong to the genus due to lack of information and specimens and is treated as a doubtful species.

A revision of Mallotus section Mallotus in Malesia is given. Descriptions, distribution maps, habit drawings and a key to all species are provided. The diagnostic characters for the section are briefly discussed. Four species (M. barbatus, M. macrostachyus, M. mollissimus, M. paniculatus) and one variety (M. paniculatus var. formosanus) are recognised.