Ongoing taxonomic studies of Australian marine algae have led to the recognition of a new species of the green algal genus Rhipilia, here named R. psammophila Huisman & Verbruggen. The new species is unusual for this typically tropical genus in growing in the colder temperate waters of southern Australia and can be distinguished from its congeners by the morphology of its laterally adhering siphons, in addition to unique molecular sequences (rbcL and tufA). In molecular analysis, the new species is sister to the southern Australian Chlorodesmis baculifera, which is here transferred to Rhipilia and represents the third species in the genus with laterally unattached, free siphons, a feature that previously would have excluded it from the genus. Lateral gametangia are described for R. psammophila and represent the first record of reproduction in Rhipilia.

An updated account of Thailand’s maidenhair ferns, Adiantum L. (Pteridaceae), is presented. The genus consists of 20 taxa, including 19 indigenous and 1 naturalised, distributed in various habitats throughout Thailand, and 5 of them are endemic. We accept A. fragiliforme and A. ciliatum as distinct species on the basis of our investigation. We also accept infraspecific taxa within A. philippense, namely A. philippense subsp. philippense and A. philippense subsp. intermedium. Revised descriptions of A. fragiliforme and A. gomphophyllum from southern Thailand are provided, as is an updated key to the species of Adiantum in Thailand, and vernacular names and conservation status assessments.

The velvet-leaf hibiscus, Hibiscus krichauffianus F.Muell. (Malvaceae subfamily Malvoideae), is predominantly associated with sand dunes in the Australian arid zone but the name is presently also applied to plants occurring in different habitats on the southern edge of the range, and in disjunct locations in Western Australia and eastern Queensland. We investigated the morphological and environmental variation within H. krichauffianus throughout the geographic range. As a result, we have identified two new species, H. verecundus McLay & Albr. and H. calcareus McLay & Albr.; coined a phrase name, H. sp. Belele (D.W.Goodall 3417) for a putative new taxon; and recircumscribed H. krichauffianus. We also assessed material collected when the protologue of H. krichauffianus was published in the late 1850s and selected a lectotype from the original material identified.