Wood anatomy of the vanguerieae (Ixoroideae-Rubiaceae), with special emphasis on some geofrutices

The Vanguerieae is a tribe consisting of about 500 species ordered in 27 ge nera. Although this tribe is mainly represented in Africa and Madagascar, V anguerieae also occur in tropical Asia, Australia, and the isles of the Pac ific Ocean. This study gives a detailed wood anatomical description of 34 s pecies of 15 genera based on LM and SEM observations. The secondary xylem i s homogeneous throughout the tribe and fits well into the Ixoroideae s.l. o n the basis of fibre-tracheids and diffuse to diffuse-in-aggregates axial p arenchyma. The Vanguerieae include numerous geofrutices that are characteri sed by massive woody branched or unbranched underground parts and slightly ramified unbranched aboveground twigs. The underground structures of geofru tices are not homologous; a central pith is found in three species (Fadogia schmitzii, Pygmaeothamnus zeyheri and Tapiphyllum cinerascens var. laetum) , while Fadogiella stigmatoloba shows central primary xylem which is charac teristic of roots. Comparison of underground versus aboveground wood shows anatomical differences in vessel diameter and in the quantity of parenchyma and fibres.