Within the rain forests of New Guinea there are many small pachycaul treelets belonging to the Rubiaceae. Generally these are rare in occurrence and poorly represented in the herbarium, due in part to the problem of protecting rami- or cauliflorous flowers and fruits during routine processing and storage. All have a similar general appearance and are difficult to assign to a particular genus. Indeed, the generic limits and relationships of many have been in doubt since they were described and few have been re-investigated in light of more recent collections and ideas. Versteegia and Maschalodesme are two of the better known genera. These are considered from a taxonomic point of view together with notes on the wood anatomy and cuticular structures. The other genera are less well known and include Airosperma in the Alberteae and many problematic species and genera in the Psychotrieae. These are distinct from both Maschalodesme and Versteegia and are not considered in the present paper.