BARK STRUCTURE AND INTERGENERIC RELATIONSHIPS OF SOME SOUTHERN AFRICAN CASSINOIDEAE (CELASTRACEAE)

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