The southem African tree, Dahlgrenodendron natalense, previously ascribed to the genus Beilschmiedia was recently segregated as a monotypic genus, Dahlgrenodendron, on account of its distinctive exomorphology, palynology and fruit structure. Dahlgrenodendron differs from Beilschmiedia in nearly all quantitative and qualitative features of wood and bark anatomy. The overall structural pattern of these tissues does not support the initial assignment of Dahlgrenodendron to the tribe Cryptocaryeae, nor does it fit any other lauraceous taxon. Within Lauraceae, an isolated non-aligned status is provisionally proposed for the genus.
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- Author or Editor: A. E. Van Wyk x
H. G. Richter and A. E. Van Wyk
M.J. Potgieter and A.E. van Wyk
A description of the bark structure of southern African species of Apodytes and Cassinopsis is presented for the first time. Bark anatomy was found useful in distinguishing between species, especially in the genus Apodytes. Fibres, associated with sclereids, are found exclusively in Apodytes spec. nov. B, whereas A. dimidiata subsp. dimidiata and Apodytes spec. nov. A contain only sclereids. Fibres are abundant in Cassinopsis tinifolia, but sparse in C. ilicifolia. Wreathing of the sclerenchyma by calcium oxalate crystals occurs in all three species of Apodytes, but not in Cassinopsis. Apodytes contains prismatic crystals as opposed to druses in Cassinopsis. Apodytes dimidiata subsp. dimidiata and Apodytes spec. nov. A show a prismatic crystal arrangement, consisting of crystalliferous cells with a large centralised prismatic crystal surrounded by numerous small peripheral crystals. Chambered cystalliferous strands occur in Cassinopsis, but not in Apodytes. Bark anatomically Apodytes spec. nov. A shows a closer correlation with A. dimidiata than with the other species.
Ekaterina L. Kotina, Patricia M. Tilney, Abraham E. van Wyk, Alexei A. Oskolski and Ben-Erik van Wyk
A remarkable, almost fur-like “indumentum” of velvety “hairs” (sometimes referred to as “fungi”) occurs on the roots (and to a lesser extent also on the trunk) of Lannea schweinfurthii var. stuhlmannii and is known as vhulivhadza in the Venda language (Tshivenḓa). The hairs are traditionally used by the Venda people (Vhavenḓa) of the Limpopo Province of South Africa, for various biocultural purposes. A detailed anatomical study of the origin, structure and development of these unusual “hairs” showed that they are of peridermal origin and develop from dense clusters of phelloid cells which are scattered within the stratified phellem. These cells are capable of considerable radial elongation thus forming hair-like radial files of elongated phelloid cells. The “hairy” patches on the bark may also develop from lenticels which become hypertrophied. These clusters of phelloid cells resemble the hyperhydric tissue which is reportedly formed in periderm of stems exposed to a water-saturated environment in some plant species. The formation of hyperhydric-like tissue in roots and stems of L. schweinfurthii var. stuhlmannii occurs, however, under relatively arid conditions. Since this tissue contains large intercellular spaces, it may also be regarded as a specialized type of aerenchymatous phellem. The adaptive significance, if any, of the phelloid “hairs” remains unknown.