Several of the species of Polysphaeria were described originally in Cremaspora, and these genera are very similar; see the key below to separate them. Cremaspora has been reported from Madagascar by various authors but Verdcourt in his 1981 study of this genus stated that it is not known from Madagascar.
Polysphaeria is characterized by its articulated petioles; interpetiolar triangular stipules that are often deciduous; axillary inflorescences that are generally sessile and capitate or glomerulate, but sometimes pedunculate and occasionally branched to 1 or 2 orders; bracts that are often fused in pairs; bisexual, fragrant flowers with 4-5 calyx lobes, corolla lobes, and stamens; funnelform mostly white corollas with the lobes left-contorted in bud; a single stigmatic club; a 2-locular ovary with the ovules solitary and pendulous from the upper part of the locule; indehiscent leathery fruits; and rather large seeds with the testa densely striate-sulcate and the endosperm densely ruminate. Verdcourt (1981) studied Polysphaeria, and recognized 9 native species in Madagascar along with another native species that he did not name, but called "sp. A". All the native species of Polysphaeria in Madagascar are endemic to the island; two species from the African mainland, Polysphaeria lanceolata Hiern and Polyspherica multiflora Hiern, do reach the Comores and also have occasionally been cultivated elsewhere, and Verdcourt (1981: p. 126) reported that Polysphaeria multiflora subsp. multiflora was at one time cultivated by the French in Madagascar.
Verdcourt (1981: pp. 99-102) presented a generalized key to Polysphaeria, but his key can be problematic to use in some cases because it depends heavily on leaf size, and the measurements given in the key do not always agree with the measurements in the descriptive comments of the individual species in this same work. Verdcourt cited one specimen for his "Polysphaeria sp. A" (1981: p. 103), Service Forestier 13793 (P) from Belambo-Manobeara. Verdcourt considered the name Polysphaeria congesta (Baill.) Cavaco, which is based on a type from the Comores, to be a synonym of Polysphaeria multiflora but he noted also that this name has been widely applied incorrectly to several native species of Madagascar.
The key below separates the species that were delimited and documented by Verdcourt (1981). Recent herbarium identifications have considered several species to have a significantly expanded range, in particular some specimens from the eastern coastal region have been identified as Polysphaeria maxima, which Verdcourt reported only from northwestern Madagascar in the area of Nosy Be and the adjacent mainland. Such new identifications are provisionally excluded from the geographic summary presented here. Verdcourt noted in 1981 that several additional undescribed species of Polysphaeria were known from Madagascar, and no doubt more such species have been documented since then. The summary here intends to compile the information documented in the last comprehensive study of this genus; the number of species and their known distributions will certainly change extensively when Polysphaeria is re-studied in the future.