Taxonomy of the genera baseonema, batesanthus, mangenotia, mondia, sacleuxia, sarcorrhiza and zacateza (Periplocoideae, apocynaceae)

[摘要] English: Seven genera of the African Periplocoideae namely: Baseonema Schltr. &Rendie, Batesanthus N.E. Br., Mangenotia Pichon, Mondia Skeels, SacleuxiaBaill., Sarcorrhiza Bullock and Zacateza Bullock are presented in this study,with special reference to taxonomy.A complete account of taxonomic literature, keys as well as knowngeographical distribution of the seven genera is given. The type specimens(in red) and all other specimens studied are presented in Appendix B.The character states and/or features used to delimit genera arecircumscribed. Floral and vegetative morphology have been extensivelystudied with the aid of a stereo-microscope and represented in the form ofdiagrammatic sketches or photographic figures. Floral (i.e. corolla, corona,androecium and gynoecium) features are important to delimit betweenspecies. For instance, Sacleuxia tuberosa is characterised by having a hairyovary and the anthers in Mangenotia are hairy. Mondia whitei has anobcordate corona lobe with two dorsal processes. Most of the genera co-existas shrubs and very rarely lianas, but Sarcorrhiza is outstanding as anepiphyte.To complement traditional taxonomy, pollen and translator morphology, leafand seed morphology have been studied, with the aid of LM, SEM and TEM.The pollen is uniform in morphology, with all the genera having pollen intetrads and little variation between the species. However, pollen grain sizecan be used to a certain extent so as to distinguish between species, forexample, the largest tetrads are found in species of Baseonema gregorii &Mondia whitei (Figure 4). One other important feature is the number of poresper grain. Most of the Periplocoids are characterised by having 4-6 pores pergrain. This, however, does not apply to multi-parate Baseonema having 8-10pores per grain, a character so far only known in species of Raphionacmeand Schlechterella. Individual grains of a tetrad are held together by wallbridges. The exine is smooth and consists of an outer homogenous stratum(tectum) subtended by a granular stratum. The intine is well developed. Thelayers turn out to be of little taxonomic value.Translators are similar in structure, with three parts distinguished, the spoon,the stalk and an adhesive disc (viscidium). The whole translator varies in size(although marginal difference is small) within the species (Table 4.2).The character state of taxonomic value in the leaf surface is the presence ofpapillae in Mangenotia eburnea. The cuticle on the leaf is variously striated orsmooth.The paracytic stomata and smooth or warty, unicellular trichomes have beenfound to be of little taxonomic value especially at generic level. However, atspecies level, the amphistomatous condition of Sacleuxia tuberosa might beof taxonomic value. Trichomes are present on the leaf surface of all taxaexcept for Batesanthus parviflorus and Batesanthus purpureus with glabrousleaf surface.Seeds are characterised by having a coma of hairs. The exception isBatesanthus intrusus with a fringe of hairs around the entire margin.

[发布机构] University of the Free State