Wood Anatomy of the Predominantly African Representatives of the Tribe Psychotrieae (Rubiaceae-Rubioideae)

Abstract

Wood samples of representatives of Chassalia, Chazaliella, Gaertnera, Hymenocoleus, Pagamea and Psychotria are examined. The generic delimitation of these predominantly African Psychotrieae, which is mainly based on fruit morphology, is compared with wood anatomical variation patterns. Part of the variation observed is related to habit, e. g. wide vessels in the tree species Psychotria dermatophylla. Other features do have systematic significance, as shown by a cluster analysis of the data obtained. The genus pair Gaertnera/Pagamea differs obviously from the other genera and is wood anatomically clearly distinguished by the presence of fibre-tracheids and parenchyma bands. Chassalia, Chazaliella, Hymenocoleus and Psychotria have rather similar wood structure, although variation in vessel diameter, vessel arrangement, ray composition and axial parenchyma occurs. Several uncommon features are recorded: the presence of few to numerous openings in one oblique perforation plate, irregular reticulate perforation plates and multiple vessel-ray perforations with marked irregularity.