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Among the tropical woody bamboos, the Melocanninae is one of the most clearly recognized subtribes morphologically and has also been consistently well delimited in molecular phylogenetic work. The relationships among those genera in this subtribe, however, have been contentious because of poorly understood generic delimitations, in part due to poor specimen material or insufficiently assessed morphological traits, sometimes exacerbated by poorly accessible provenances. We address the phylogenetic and taxonomic status of two groups which together include the largest number of species in this subtribe: the Neohouzeaua-Schizostachyum complex, distributed from India to South China, Southeast Asia and southwest Pacific, and the endemic Indian genus Ochlandra. Three Neohouzeaua species (including the generic type), 12 Schizostachyum species (including the generic type and several species of uncertain placement), together with five species of Ochlandra and representatives of Cephalostachyum, Melocanna and Pseudostachyum were assessed in a molecular phylogenetic analysis together with members of other well-distinguished subtribes. Members of Neohouzeaua and Schizostachyum align into two main groups that were not completely well-supported statistically but which members possess mostly reflexed culm leaf blades, or mostly erect culm leaf blades. Other characters which provide obvious differences between taxa, such as the number of flowers in a pseudospikelet, fusion of filaments into a staminal tube, and presence of lodicules, were inconsistent between these groups. Neohouzeaua and Schizostachyum cannot be clearly distinguished in either morphological or molecular terms, and thus are united under the latter name, which takes precedence. In reviewing names in Neohouzeaua and their basionyms, several lectotypifications are designated. Three new combinations in Schizostachyum are proposed. On the other hand, Ochlandra forms a distinct clade and its monophyly is demonstrated, supported by clear morphological characters.

As part of a revision of Timonius in Borneo, the types of all relevant names were evaluated. Lectotypes are designated for 14 names in Timonius, including synonyms for accepted names. An erroneous original type citation is corrected and the nomenclatural history of a few names is clarified.

In the most recent revision of the genus Melastoma Linnaeus (1753: 389) across its entire distributional range, seven species were recognized for Peninsular Malaysia and Singapore (Meyer 2001). Our recent studies in Southeast Asian Melastoma have led us to re-examine some of the species defined in that account, including those recorded for Peninsular Malaysia and Singapore (Wong 2015, Wong 2016, Neo et al. 2017).

Canthium longipetalum Y.H.Tan & S.S.Zhou in Yang et al. (2019: 197) is a species of Rubiaceae recently described from northern Myanmar. This species was identified as belonging to the Vanguerieae tribe, and was placed provisionally in the genus Canthium Lamarck (1783: 602) based on morphological characters including the presence of axillary inflorescences, valvate corolla aestivation, two-locular ovaries, and a two-lobed stigma (Yang et al. 2019). However, the suite of characters cited by the authors to support the placement of their species in Canthium define an overly broad and now-superseded concept of the genus.

A new species, Urophyllum malayense (Rubiaceae) is described, endemic to the Malay Peninsula (Peninsular Malaysia and Singapore). It has resemblances to Urophyllum trifurcum but differs notably in the extent of inflorescence branching and flower size.

Phai Liang, a recent bamboo cultivar originating in Thailand and widely introduced to many parts of Malaysia and Singapore, has yet to be diagnosed scientifically. In this study, the partial nuclear Granule Bound Starch Synthase I (GBSSI) gene of Phai Liang was cloned and sequenced to investigate its hybrid origin. Its morphological characteristics were compared with those of its putative parental taxa. Based on both molecular and morphological evidence, Phai Liang is recognized as representing a new nothogenus and nothospecies, ×Thyrsocalamus liang. This circumscribes a hybridization complex with variable morphological characters which reflect different degrees of intergradation between the parental species, Dendrocalamus membranaceus and Thyrsostachys siamensis.

Melastoma kemamanense is here described as a new species. It is characterised by broad, scabrid leaves, twigs with closely appressed scales, flowers in compact cymes, and anisomorphic stamens. It is similar to Melastoma imbricatum but differs from it by the thickly overlapping hypanthium scales and larger mature fruits. This new species is so far only known from northeast Peninsular Malaysia.

Schizostachyum cambodianum is a new species of woody bamboo from the Cardamom Mountains in Cambodia. It is instantly recognized by a very large suborbicular projection at the base of the culm sheath. The only other bamboos which are known to consistently show such similar suborbicular projections are the Chinese species Schizostachyum hainanense, S. auriculatum, and S. dumetorum. In these species, however, the projections are less than one cm wide, whereas in S. cambodianum, it is particularly impressive, developing to about 3 cm wide. S. cambodianum can further be distinguished from its Chinese relatives by forming lax clumps due to its long-necked rhizomes and largely glabrous culm sheaths with only scattered pale hairs.

Schizostachyum langbianense is a new woody bamboo from a high mountain, Lang Bian, in southern Vietnam, which is being described and illustrated. It is similar to S. ninhthuanense in having short ultimate inflorescence branchlets on which clusters of a few pseudospikelets are borne. However, it differs in its culm leaves with a horizontal or only slightly concave apical portion, culm leaf blades that are narrowly lanceolate, and a palea that is not apically bifid and dorsally sulcate with 2 keels. Both species occur in the same mountain region, but separated by distinct elevations.