Mad Cat: Chassalia is the correct spelling. Evaluation is based on the specimens from TAN and TEF only.
CMT: This genus was studied in Madagascar and the Comores by Bremekamp (1962), and Verdcourt (1983) later reviewed it in the Mascarenes and provided some important comments. The spelling of this genus name has varied, and in fact Bremekamp spelled the genus name incorrectly in his work. Bremekamp reported only one species from the Comores, but there now appear to be at least two more (e.g., O. Pascal 277; W.G. D'Arcy 17613, 17669) with one or more of these perhaps shared with Madagascar but that remains to be studied. Bremekamp recognized 32 species of Chassalia in this region, with 1 species endemic to the Comores and 31 endemic to Madagascar. The most commonly collected species are Chassalia princei and Chassalia bojeri, which are rather similar but differ in corolla size and habitat. The species-level here was compiled by the Mad Cat, and has not been revised by CMT: this information may be correct, but specimens of Chassalia are often misidentified, and not all the specimens studied by the Mad Cat are available to CMT at this time. CMT's species-level contribution is limited to text comments and the TROPICOS data for specimens deposited at MO, and the species circumseripitons here often differ from the taxonomy used by several other workers.
Chassalia is characterized by its woody habit; tissues with raphides; opposite to verticillate leaves; stipules that are interpetiolar or shortly fused around the stem and on each interpetiolar side triangular to bidentate, and generally are persistent or deciduous via fragmentation with the persistent portions becoming dried or indurated; terminal cymose inflorescences that are generally pedunculate with reduced bracts; bisexual, generally 5-merous flowers; white to pink, slenderly salverform corollas that are often curved in the tube and occasionally longitudinally winged in the upper portion at least in bud, with the lobes valvate in bud and sometimes horned; and fleshy, purple to black, drupaceous fruits with two stiffly papery to hard pyrenes that are concavo-convex or planocovex with a fairly deep adaxial excavation. The corollas usulaly have a well developed tube, and in some species they characteristically markedly just before anthesis so measurements inferred from buds are not always reliable. At least some species of Chassalia may be nocturnal, although the floral biology of this genus has not been documented. Bremekamp characterized species as isostylous or distylous based on the relative position of the anthers and stigmas, but this has not been studied in the field. Most species of Chassalia have a characteristic infructescence, with the pedicel or axis supporting the fruit becomeing thickened and brightly colored, usually purple. Presumably this is an adaptation for bird dispersal; it is rare in other genera, but found also in a few species of Psychotria in Madagascar (.e.g, Psychotria rubropedicellata). The leaves of most species are opposite, but a ternate or 4(5)-verticillate characterizes in several species. Bremekamp noted that the number of leaves per node varies in these ternate or verticillate species, and that in some species that characteristically have opposite leaves there are occasional individuals with ternate leaves (e.g., Chassalia bojeri); whether the species he characterized by having verticillate leaves are distinct from simliar species characterized as having opposite leaves remains to be evaluated. Chassalia is similar to Psychotria, and these are often confused. They can be separated by stipule and pyrene form, and also sometimes by the red or white fruit color of some Psychotria species. See the Mad Cat Psychotria page for a key to these and other similar genera.
Bremekamp (1962) used floral biology, isostylous vs. distylous, as the main distinction in his key thus fruiting specimens are difficult to identify using his treatment. Bremekamp separated two subgenera, Chassalia subg. Chassalia with well developed leaves and most of the species, and Chassalia subg. Microphyllum with quite reduced leaves. The reduced leaves of several of the species of Subg. Microphyllum are distinctive, and these are similar unusual species of some other Rubiaceae genera in Madagasar (e.g., Gaertnera, Psychotria, Saldinia, Schismatoclada), several of which are found in same region; these are separated by subtle characters and often confused, with the species of Chassalia often overlooked.