Notes on the genus Cercestis (Araceae) and a new species from Liberia: Cercestis hepperi Jongkind sp. nov.

In early 2009 two different hard-to-identify Cercestis species were collected near Sapo National Park in Liberia. They did not fit well in any of the species that were left in the genus after the work of Ntépé-Nyamè on the Araceae for the Flore du Cameroun (Ntépé-Nyamè 1988). Comparing the new material with collections in the Kew herbarium resulted in the discovery of several other specimens of one of these species, described as C. hepperi sp. nov. below. This species proved to belong to the same taxon as the material labeled as ‘‘Cercestis near kamerunianus (Engl.) N. E. Br., note yellow margin’’ by Hepper in 1966 in the Kew herbarium (Hepper 1968, p. 127). However, the inflorescences of C. kamerunianus, a species from central Africa that has become better known since Heppers observation, are much smaller and shorter than those of C. hepperi. The peduncle of the inflorescence of C. kamerunianus is 3.06.5 cm long while that of C. hepperi is 714 cm long. The leaves of these two species are also different in shape; the leaves of C. kamerunianus are much narrower above the basal lobes than those of C. hepperi (Ntépé-Nyamè 1988, p. 74). Cercestis hepperi differs from C. ivorensis A. Chev., a related species that grows in the same area, by its longer inflorescences and conspicuous yellowish leaf margin, the peduncle of the inflorescence of C. ivorensis is 35 cm long while that of C. hepperi is 714 cm long. Cercestis ivorensis often has some of its leaves with a truncate base while the leaf base of C. hepperi is always cordate. The second hard-to-identify Cercestis species from Sapo National Park proved to be identical to C. sagittatus Engler, a taxon that was synonymised with C. dinklagei by Ntépé-Nyamè (1988, p. 66). However, the infructescences of the type of C. sagittatus are different from those of C. dinklagei and the plant is more robust, as already stated by Hepper (1968, p. 126, with C. dinklagei under its former name C. stigmaticus N. E. Br.). The mature infructescence of C. sagittatus resembles those of C. afzelii in remaining entire at maturity while those of C. dinklagei, C. ivorensis and C. hepperi more-or-less comes apart when the central column becomes soft and the individual fruits easily drop. This difference in the infructescences seems to be connected with the way the plant grows, C. afzelii and C. sagittatus are reported to be robust climbers while C. dinklagei, C. ivorensis and C. hepperi remain closer to the forest floor.