Contributions to the wood anatomy of the Rubioideae (Rubiaceae)

The secondary xylem of Craterispermeae, Coussareeae, Morindeae s.str., Pris matomerideae, Pauridiantheae, Urophylleae, and Triainolepideae (Rubiaceae, Rubioideae) is described and illustrated in detail. Genera that were previo usly placed in the Morindeae or Psychotrieae such as Damnacanthus, Lasianth us, Saldinia, and Trichostachys are also included. Wood anatomical characte rs are compared with recent phylogenetic insights into the study group on t he basis of molecular data. The observations demonstrate that the delimitat ion and separation of several taxa from the former Coussareeae/Morindeae/Pr ismatomerideae/ Psychotrieae aggregate is supported by wood anatomical data . The Coussareeae can be distinguished from the other Rubioideae by their s canty parenchyma, septate libriform fibres, and the combination of uniseria te and very high multiseriate rays with sheath cells. Axial parenchyma band s and fibre-tracheids characterise Gynochtodes and some species of Morinda (Morindeae sstr.), but the latter genus is variable with respect to several features (e.g. vessel groupings and axial parenchyma distribution). Wood d ata support separation of Rennellia and Prismatomeris from Morindeae s.str. ; vessels in both genera are exclusively solitary and axial parenchyma is a lways diffuse to diffuse-in-aggregates. Damnacanthus differs from the Morin deae alliance by the occurrence of septate fibres, absence of axial parench yma, and the occasional presence of fibre wall thickenings. There are inter esting similarities between members of the Lasianthus clade and the Pauridi antheae/ Urophyleae group such as the sporadic occurrence of spiral thicken ings in axial parenchyma cells.