Pauridiantha Hook.

Salvator NTORE & Olivier LACHENAUD, 2019, Two new species and a new combination in the genus Pauridiantha Hook. f. (Rubiaceae) from tropical Africa, Adansonia 41 (4), pp. 29-40 : 31-32

Pauridiantha Hook. f.

In Genera Plantarum 2: 69 (1873). —

Typus: P. canthiiflora Hook.f.

Rhipidantha Bremek., Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie 71: 222 (1940), syn. nov. —

Typus: R. chlorantha (K.Schum.) Bremek.

REMARKS

Rhipidantha has always been regarded as a monospecific genus endemic to the Uluguru Mountains of Tanzania. Its only species was originally described in Urophyllum Wall. ( Schumann 1899: 57) before Bremekamp (1940) erected a new genus for it. Bremekamp separated Rhipidantha from Pauridiantha by its (4-)5-locular ovary (vs 2-locular in Pauridiantha ), and from Poecilocalyx by its lax and pedunculate inflorescences, dentate (vs deeply lobed) calyx, sessile stigmas (actually connate into a style, though very shortly so in brevistylous flowers) and absence of conspicuous indumentum. Verdcourt (1976) accepted the genus as distinct from Pauridiantha , chiefly based on the number of ovary locules, but the subsequent inclusion of Commitheca (with 2- to 4-locular ovaries) and Poecilocalyx (with 2- to 5-locular ovaries) in Pauridiantha makes this character no longer reliable. In fact, on morphological grounds Rhipidantha is even closer to Pauridiantha s.str. than are Poecilocalyx and Stelechantha (both of which are now included in Pauridiantha ), and its great similarity to Pauridiantha insularis (Hiern) Bremek. has already been noted by Ntore (2008: 109). The fruits and seeds of Rhipidantha , previously unknown, have recently been collected and also agree very well with the genus Pauridiantha - the seeds in particular ( Fig. 1A, B ) are extremely similar to those of P. insularis , illustrated in Ntore (2008: fig. 29). Therefore, despite the absence of molecular data for Rhipidantha , there can be no reason for keeping the two genera separate.

KENYA DEMOCRATIC REPUBLIC OF THE CONGO

TANZANIA

500 km

The inclusion of Rhipidantha in Pauridiantha requires the new combination below. Since R. chlorantha is rather little-known and its previous descriptions ( Schumann 1899; Bremekamp 1940; Verdcourt 1976) were incomplete on several points, a complete and updated account of this species is presented here.

Figures

FIG. 1. — Seeds of Pauridiantha chlorantha (K.Schum.) Ntore & O.Lachenaud, comb. nov., from Jannerup & Mhoro 129 (A, B) and P. gracilipes O.Lachenaud & Ntore, sp. nov., from Lachenaud et al. 1981 (C, D) in electron microscopy: A, C, entire seed; B, detail of exotesta cells with outer tangential wall removed, showing thickened radial walls with small pits, and large pits in the inner tangential walls; D, detail of exotesta cells with outer tangential wall removed, showing thin radial walls with small pits, and large pits in the inner tangential walls. Scale bars: A, C, 100 µm; B, D, 10 µm.