Taxonomic significance of pericarp and seed structure in Weeria argentea (Thunb.) Meisn. (Anacardiaceae) including reference to pachychalazy and recalcitrance

He& urgentea (tribe Rhoeae), a monotypic, dioecious tree, is endemic to the core area of the Cape Floristic Region. The mature exocarp consists of a uniseriate layer of palisade-like epidermal cells, interspersed with modified stomata. The mature endocarp sensu slricto develops solely from the inner epidermis. It is essentially two-layered and resembles the state in Frotorhw longiiolzu. This endocarp is here proposed as a distinct fourth endocarpal subtype under the so-called Anacardzum-type. The large, pachychalazal, recalcitrant seed develops from the single, anatropous, bitegmic, crassinucellate ovule. This ovule is characterized by an extensive chalaza, sascularization and Anacardiaceae-type hypostase. The pachychalazal seed coat contains abundant vascular bundles and a tanniniferous hypostase. The inner epidermis of the inner integument differentiates into an endotegmen. The contribution of the integuments towards seed coat development is negligible. Concerning characters of the disc in the female flower, the meso- and endocarp, as well as seed size, degree of pachychalazy, nutrient reserves (starch) in the chlorophyllous cotyledons and hrpogeal germination, Hem'a shows a sexy close phylogenetic relationship to Frotorhus longifoolia. However, fruit and seed structure clearly supports the taxonomic separation of He& from Oz070a. Data also support the view that He& is a tropical relict, and the hypothesis that pachychalazy, greater seed size, as well as recalcitrant seed viability behaviour constitute ancestral seed character states. Pachychalazy is regarded as a functional adaptation for more efficient transfer of nutrients.