Wood and bark anatomy of the african species of

Quantitative and qualitative data are given for the two African species of Gnetum (Gnetum section Gnetum subsection Micrognemones). These species are lianoid and lack the fibre-tracheids of G. gnemon but have about the same vessel element and tracheid length as in that species. Vessel diameter is related to stem age and organography. Tori are clearly present in tracheary elements of the African Gnetum species, a first report for the genus. In these two species, origin of the lateral meristem, which produces vascular tissue and cambia, can be traced directly and indirectly to cortical parenchyma. A second kind of meristematic action, newly reported for Gnetum, is produced by proliferation of axial parenchyma, fragmenting secondary xylem. Both presence of tori and site of origin of lateral meristematic activity in Gnetum contrast with corresponding conditions in Welwitschia.