The present investigation has been carried out in the “Botanisch Museum en Herbarium” of the University of Utrecht. I wish to render to Dr. A. Pulle, the Director of the Institute, my most sincere thanks for the facilities afforded to me and for the interest in the progress of this work. I am also greatly indebted to the Directors of the Berlin-Dahlem, Brussels, Göttingen, Leiden and Paris Herbaria and to the members of their staff for the opportunity of studying in these Institutes the collections entrusted to their care and for their helpful advice. Special words of thanks are due to Dr. O. C. Schmidt (Berlin-Dahlem), Dr. R. Benoist (Paris) and Dr. Exell (South Kensington). To Mr. Wilmott (South Kensington) I am obliged for the information he gave me with regard to the genus Persea, and to Dr. Hochreutiner (Geneva) for the loan of the type specimen of Ocotea vernicosa. To the Brussels, Berlin-Dahlem, Göttingen, Kew, Leiden and Paris Herbaria I am indebted for the loan of specimens which I needed for the solution of various special problems.