Dombeya Cav. (Malvaceae) as presently defined encompasses over 200 species and considerable morphological variation. Within the 2- to 3-carpellate Dombeya subg. Xeropetalum (Delile) K. Schum., almost half of the recognized species belong to Dombeya sect. Decastemon Planch., which is endemic to Madagascar and traditionally distinguished by its umbellate rather than cymose inflorescences. The most recent taxonomic treatment of this section recognized 47 species and numerous infraspecific taxa; an additional species referable to this group was recently described. The present treatment recognizes 41 species and 11 subspecies. Six species (D. micrantha Appleq., D. milleri Appleq. & Bosser, D. pauciflora Appleq., D. pilosissima Appleq. & T. Andriam., D. ratovosonii Appleq. & Bosser, D. vohemarensis Appleq.) are newly described, and one (D. ramiovensis (Arènes) Appleq. [≡ D. farafanganica Arènes subsp. ramiovensis Arènes]) is newly elevated to specific rank. Dombeya parvipetala Arènes, which (like D. pilosissima) has a small, dichotomously branching cymose inflorescence, is transferred from Dombeya sect. Xeropetalum (Delile) Planch. to Dombeya sect. Decastemon. The following names are transferred: D. ambalabeensis Arènes subsp. analavelonae (Arènes) Appleq. [≡ D. analavelonae Arènes], D. decanthera Cav. subsp. farafanganica (Arènes) Appleq. [≡ D. farafanganica], D. decanthera subsp. latipetala (Arènes) Appleq. [≡ D. farafanganica subvar. latipetala Arènes], D. subviscosa Hochr. subsp. ihosyensis (Arènes) Appleq. [≡ D. ambongensis Arènes var. ihosyensis Arènes], D. subviscosa subsp. sakarahae (Arènes) Appleq. [≡ D. ambongensis subsp. sakarahae Arènes]. Subsections formerly recognized are not reliably separable by morphology, so only six series are recognized, one of them newly described (Dombeya ser. Pentandrae Appleq.) and one newly recognized at that rank [Dombeya ser. Decantherae (Arènes) Appleq.]. Placement of species into series has been greatly rearranged, although some series remain heterogeneous and are used for convenience with no assertion of probable monophyly. Consistent with published reports of hybridization in other subgroups of Dombeya, a number of probable hybrid specimens are noted, several of readily identifiable parentage, but are not nomenclaturally recognized.

Thirty-four species representing all subfamilies and tribes of the Rutaceae Juss. were included in phylogenetic analyses that utilize six molecular data sets from five chloroplast markers, three from the noncoding region (the rps16 gene intron, the trnL–trnF intergenic spacer, and the atpB–rbcL spacer) and two from coding genic regions (rbcL, atpB), with the sixth marker from the Xdh nuclear gene. Based on the large number of nucleotide characters from the chloroplast and nuclear regions as well as the high levels of resolution and support from both parsimony and Bayesian analyses, the results are sufficiently robust to justify reclassification of the Rutaceae, with four subfamilies recognized in contrast to the traditional seven. This subfamily classification includes major rearrangements: (1) taxa within the subfamily Aurantioideae Horan. remain the same; (2) subfamily Cneoroideae Webb encompass the subfamilies Spathelioideae Engl. and Dictyolomatoideae Engl., Harrisonia R. Br. ex A. Juss. of the Simaroubaceae DC., Cneorum L. of the Cneoraceae Vest, and Ptaeroxylon Eckl. & Zeyh. of the Ptaeroxylaceae J.-F. Leroy; (3) subfamily Rutoideae Arn. include Ruta L. and Chloroxylon DC. of subfamily Flindersioideae Luerss.; and (4) subfamily Amyridoideae Link unite Flindersia R. Br. of subfamily Flindersioideae with subfamily Toddalioideae K. Koch and taxa previously included in subfamily Rutoideae.

This paper provides identification keys that are based entirely on morphological features to commonly and widely cultivated eucalypts, encompassing Eucalyptus L'Hér., Angophora Cav., and Corymbia K. D. Hill & L. A. S. Johnson in the Myrtaceae Juss. The key includes 173 taxa: one species of Angophora, nine species of Corymbia, and 163 species of Eucalyptus. Evidence for cultivation was determined by accounts in the literature, herbaria, personal communications, and observations of living trees in cultivation in Europe, North America, Africa, and Australia. The locations, prevalence of cultivation, and naturalization of several eucalypt species are discussed.

Gaertnera Lam. (Rubiaceae, Gaertnereae) includes 42 species confirmed from Madagascar, with 16 of them newly described here as a result of recent botanical exploration. The Madagascar species of Gaertnera have notable morphological variation. Newly described, illustrated, and keyed here are G. arenarioides C. M. Taylor, G. breviflora C. M. Taylor, G. hirsuta C. M. Taylor, G. laevis C. M. Taylor, G. littoralis C. M. Taylor, G. malcomberiana C. M. Taylor, G. masoalana C. M. Taylor, G. nitida C. M. Taylor, G. rakotovaoana C. M. Taylor, G. razakamalalana C. M. Taylor, G. robusta C. M. Taylor, G. rubra C. M. Taylor, G. sclerophylla C. M. Taylor, G. velutina C. M. Taylor, G. vernicosa C. M. Taylor, and G. xerophila C. M. Taylor. Narrower circumscriptions of G. obovata Baker var. sphaerocarpa (Baker) Malcomber and G. phanerophlebia Baker here are detailed by revised descriptions. Assessments of conservation status of Gaertnera in Madagascar using IUCN categories find two species Critically Endangered, 10 Endangered, 14 Vulnerable, two Near Threatened, and 14 species and two varieties of Least Concern.