At the instigation of the Director of the “Rijksherbarium” at Leiden, Prof. Dr H. J. Lam, who was puzzled by the problem of the delimitation of the genus Isonandra towards other genera, especially Palaquium, I assumed the task to compose a monograph of Isonandra. For this study material was kindly put at our disposal by the directors of several institutes, which enabled me to check up the type-specimens of all species, except that of Isonandra emarginata H. J. Lam, which failed to turn up even at Singapore and at Borneo. However, the Isonandra-character of this species is doubtful: it is more like Palaquium. It is my pleasant duty to express my sincere thanks to the directors of the institutes mentioned underneath, for their valuable cooperation. Our thanks also due to Mr T. P. Nedungadi, M. A. of the Embassy of India at The Hague, whose kind intermediary enabled me to consult detailed maps of India and Ceylon.