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Notes:
This genus is characterized (in Madagsascar) by its woody habit; leaves that often have domatia; interpetiolar, triangular, generally awned and persistent stipules; axillary, several-flowered, fasiculate to shortly cymose and subsessile inflorescences with the bracts usually fused in pairs; mostly four- to five-merous, unisexual flowers on dioecious or gynodicecious plants; truncate or denticulate calyx limb; somewhat small, white, salverform corollas that have usually pubescence at the stamen attachment but are not densely bearded in the throat, and have the lobes contorted to the left in bud; exserted anthers with a small, generally triangular apical appendage; two exserted linear stigmas; and fleshy, subglobose, drupaceous fruits that become red when mature and have 2-16 somewhat flattened seeds (or pyrenes?). The a pair of opposite bracts or bracteoles that is fused creates the cupular structure called a calyculus, or sometimes a cupule (e.g, FTEA); calyculi are characteristic of Tricalysia and Coffea. The most commonly collected and widely distributed species in Madagascar is Tricalysia cryptocalyx.
Tricalysia has several distinct taxonomic groups with numerous species and notable morphological variation in Africa. The species of Tricalysia from Madagascar are classified in their own group, Tricalysia sect. Androgyne, which differs from the rest of the genus in having unisexual flowers on dioecious or gynodioecious plants and may be monophyletic (Tosh et al., 2009). In the revision of Tricalysia in Madagascar, Ranrivelo-Randriamboavonjy et al. (2007) included one species, Tricalysia ovalifolia, that does not belong to Sect. Androgyne and has since been separated into another genus, Empogona; the species of Empogona were previously included in Tricalysia, but morphological and molecular data support the separation of these two genera (Tosh et al., 2009).
Tricalysia is similar in aspect to some species of Ixora, which has four-merous flowers and petioles that are articulated at the base. Tricalysia is very similar to Coffea, which has bisexual flowers, the calyx limb sometimes reduced to a thin rim or skirt that is shorter than the disk, and fruits with two rather planoconvex pyrenes that are adaxially sulcate; Coffea has many more species and in general is more commonly collected than Tricalysia in Madagascar. Empogona differs from Tricalysia in its usually well developed pedicels, its lobed calyx limb, its bisexual flowers, and its fruits that are black at maturity (see also the key to these genera below). Tricalysia is also similar to Cremaspora, which is found in the Comores but has not yet been documented from Madagascar, and has sessile flowers in axillary glomerules, a pubescent calyx limb with developed triangular lobes, bracts and bracteoles that are not fused in pairs, and the stigma very shortly bifid at the apex.
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