Applequist, W.L. (2018). A revision of the Malagasy species of Homalium sect. Blackwellia (Salicaceae). Candollea 73: 221–244. In English, English and French abstracts. DOI: http://dx.doi.org/10.15553/c2018v732a7

Homalium sect. Blackwellia Benth. (Salicaceae) is the largest and most widespread solitary-stamened section of Homalium Jacq. As part of a project to update the taxonomy of Homalium in Madagascar, a new revisionary treatment of the Malagasy species is presented and an identification key is provided. Fifteen species are recognized, of which four are newly described, and within Homalium axillare (Lam.) Benth. a subspecies, Homalium axillare subsp. delphinense (H. Perrier) Appleq., is recognized. Homalium acuminatifolium Appleq. is similar to Homalium axillare, but the leaves are usually lanceolate with a long-acuminate apex and the petals often spreading; it is native to the province of Toliara. Homalium longiracemosum Appleq. is distinguished by its long racemes and long, narrow, long-petioled leaves; it is endemic to the vicinity of Sainte Luce. Homalium fortunatii Appleq. and Homalium martialii Appleq. are similar to Homalium thuarsianum (Tul.) Baill. in having pubescent sepal glands and paniculate inflorescences. Both of these new species have usually elliptical to narrowly elliptical leaves and are native to northeastern humid forests. Homalium fortunatii has minutely pubescent young twigs, while Homalium martialii has sepals and petals always shorter than the calyx tube. Occasional hybridization is observed. Homalium microphyllum O. Hoffm. is not recognized and the type is believed to be a hybrid involving a species of Homalium sect. Odontolobus Warb.