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Robert H. Archer and Abraham E. van Wyk

At present Cassine in southern Africa is treated in a wide sense (s.l.), including amongst others Allocassine p. p., Cassines. str., Crocoxylon, Elaeodendron, Lauridia, and Mystroxylon. A comparative anatomical study was made of mature bark representing 16 southern African species of Cassine s.l., and the monotypic Allocassine, Hartogiella and Maurocenia (all members of the subfamily Cassinoideae). Six bark types are distinguished on the basis of the type of sclerenchymatous elements in the secondary phloem; presence or absence of styloid crystals, e1astic threads, and sclerified phelloderm; stratified homogeneous phellem; and degree of rhytidome development. These correlate to a considerable extent with the generic subdivision of Cassine s.l. proposed by Loesener (1942) and Robson (1965). On the basis of bark anatomy and other evidence, it is proposed that the circumscription of Cassine be restricted to include only the southern African species C. peragua and C. parvifolia, and possibly Hartogiella. Crocoxylon, Elaeodendron, Lauridia and Mystroxylon should be reinstated or maintained, although with some modification of the originally defined generic limits.

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Robert H. Archer and Abraham E. van Wyk

Opinions differ on whether to treat Cassine in southern Africa in a wide sense, or to recognise several segregate genera, such as Elaeodendron, Crocoxylon, Lauridia, Mystroxylon and Cassine s. str. A comparative anatomical study was made of mature wood representing 17 southern African species of Cassine s.l., Pleurostylia and the three monotypic genera, Allocassine, Hartogiella and Maurocenia (all members of the subfamily Cassinoideae). The wood structure is described with emphasis on the taxonomic value of quantitative and qualitative characters. Various features were found to be diagnostic at supraspecific level. The presence or absence of scalariform perforation plates, septate fibres, various ray types, and additional quantitative characters could be useful for taxonomic application, especially for generic delimitation. Three principal wood types, of which one encompasses three subtypes, are recognised among the species examined. Wood anatomical evidence tells against a wide generic concept for Cassine, and favours the recognition of segregate genera.