Taxonomic position of Rhus problematodes (Anacardiaceae): Evidence from fruit and seed structure

This is the first report on the structure of the pericarp and seed coat of Rhus problematodes Merxm. & Roessl., a curious microphyllous shrublet of very limited distribution in the southern desert region of Namibia. Mainly on the basis of macromorphology, it was hitherto considered to stand somewhat apart from other African members of Rhus L. (sect. Gerontogeae Engl.). R. problematodes clearly agrees with other species of Rhus in its basic pericarp and seed-coat characteristics, including a single-seeded unilocular drupaceous fruit, parenchymatous mesocarp with secretory ducts, ridged outer endocarp, inner endocarp composed of three discrete layers, and an endotegmic, partially pachychalazal seed coat. The scarcity of stomata and heavy deposition of cutin in the exocarp possibly reflect adaptations to its arid habitat. Evidence from fruit and seed structure, combined with that from other sources, reconfirms the view that it is a highly specialized species of Rhus showing several xeromorphic, mainly macromorphological, reductions. The shared presence of glandular stellate hairs and reduced foliage leaves suggests that it might be closely allied to R. horrida Eckl. & Zeyh., a species from Namaqualand

A preliminary study on the germination of Sclerocarya birrea subsp. caffra

Seeds of Sclerocarya birrea (A. Rich.) Hochst. subsp. caffra (Sond.) Kokwaro, commonly known as marula, occur in locules within a hard lignified endocarp. The endocarp appears to restrict germination mainly by offering mechanical resistance. It may also restrict the leaching of germination inhibitors and possibly serve as a barrier to oxygen diffusion. The endocarp does not restrict water uptake. High germination counts were only obtained by removing opercula. Leaching slightly improved germination of seeds in intact endocarps. The optimum germination temperature of opercula-removed seeds was between 27° and 37°C. Storage improved rate of germination

The structure of the seed of Mangifera indica L. and notes on seed characters of the tribe Mangifereae (Anacardiaceae)

The anatropous, unitegmic and pachychalazal mango ovule develops into the campylotropous, pachychalazal seed. The undifferentiated seed coat is of dual origin, developing from the integument as well as from the pachychalaza. The term ‘peritesta’ is suggested for the peripheral, band-like integumentary part of the seed coat. The major saddle-shaped chalazal part is associated with a tanniniferous hypostase. The discussion includes the anatomy and histochemistry of the seed. The pachychalazal seed with undifferentiated seed coat probably characterizes the tribe Mangifereae. After consideration inter alia of seed characters, it is concluded that, according to generally accepted criteria, the Anacardiaceae is phylogenetically one of the more advanced forest families

A morphological study of the fruit and seed of certain southern African members of the Anacardiaceae

The Anacardiaceae is a natural family which is grouped into five tribes. Two of these occur in southern Africa. The Spondieae is represented by Harpephyllum Bernh. ex Krauss, Lannea A. Rich. and Sclerocarya Hochst. and the Rhoideae by Heeria Meisn., Laurophyllous Thunb., Loxostylis Spreng. f. ex Reichb., Ozoroa Del., Protorhus Engl., Rhus L. and Smodingium E. Mey. ex Sond. Although this study focusses mainly on the three species of the Spondieae and Rhus lancea L.f., observations on other species, e.g. of Heeria, Mangifera L., Operculicarya H. Perr. and Tapirira Aubl., are also described. The thesis includes reprints and manuscripts of scientific papers, dealing mainly with the ontogeny and structure of the fruit and seed. The taxonomic significance of characters is stressed, supplemented with notes on evolutionary trends and seed germination. A comprehensive review of the literature is provided, including comments on the structure and function of the hypostase and occurrence of the pachychalaza. The exocarp of the drupe in Anacardiaceae may be thin (R. lancea) or thick, representing an exocarp sensu lato (Sclerocarya). The mesocarp is characterized by conspicuous secretory ducts and usually differentiates after endocarp lignification. The endocarp is usually a sclerocarp. It is either stratified (R. lancea) or non-stratified (Spondieae). Opercula are restricted to the members of the Spondieae with well-developed sclerocarp.Thesis (DSc)--University of Pretoria, 1988.Plant ScienceDScUnrestricte