Many species of the Pithecellobium complex have been transferred to other genera by a number of authors time and again, depending on the characters used for the segregation. The wood of Pithecellobium species shows some diversity as seen in transverse section, but many species are strikingly alike in their ray structure as seen in tangential section. In other large genera, for instance Inga of the Mimosaceae, the ray structure has proved to be of great value in classifying the species; the same seems to be true for Pithecellobium. There are many species with very low. widely spaced, and predominantly uniseriate rays; an unusual combination in Mimosaceae. Most species have thin-walled fibres. Several segregated ”genera” show the same type of wood and, therefore, their segregation does not seem justified. Pithecellobium saman (Jacq.) Benth., recently included in Pithecellobium again, shows an essentially different wood structure and should better be treated as the genus Samanea. Zygia. included in Bentham’s section Caulanthion, and now incorporated in Pithecellobium again, also differs in its wood structure from this genus. This indicates that Zygia should be reinstated on the generic level, or at least as a distinct section of Pithecellobium.