1. Introductory.--This project was to study fern specimens in certain herbaria in the U.S.A., especially of tree-ferns (Cyatheaceae), in connection with preparation of the Pteridophyte Series of Flora Malesiana, and to make contacts in the U.S.A. with a view to continued cooperation in this work. The family Cyatheaceae, on which I am at present engaged, is a particularly difficult one, comprising 350 described species in Malaysia, in a close alliance. Probably all should be regarded as belonging to one genus. Descriptions of species have on the whole been unsatisfactory, so that many identifications of specimens in herbaria are doubtful or erroneous. It is thus necessary to see all type specimens to establish the significance of names; and also, as the fronds are large so that only a part of one appears on each herbarium sheet, the different specimens of the same collection, distributed to different herbaria, often give complementary information, so that to see one is not enough. Furthermore, it is necessary to see as many collections as possible, to understand what variation is possible within a species. The material is bulky, and it is a physical impossibility to gather together in one place all that one needs to see for a proper understanding of the family. I had already spent more than a year on this study before going to the U.S.A., and had seen most of the type material in European herbaria.