On several occasions the author received specimens for determination under the name of Loranthaceae, which in reality appeared to be Phacellarias, usually parasitic on Loranthaceae. When trying to name these Phacellarias, he preceived how difficult it was to survey the literature of the genus. Though only eight species have been described, and the authors usually have indicated the main differences between their new species and the most closely allied previous ones, the most essential characteristics of the species, viz., the structures of the inflorescences, were never indicated, and a critical review of all the species has never been given. Therefore it appeared an attractive task to undertake such a revision, if only it were possible to examine all the type specimens. Through the kindness of the Directors and Keepers of the Kew and Edinburgh Botanic Gardens (K, E) and of the Paris Natural History Museum (P), the author was actually allowed to do this. Moreover he had the opportunity to study specimens of the Herbarium of the British Museum of Natural History in London (BM) and the Buitenzorg Botanic Gardens (B), whereas he discovered one specimen in Mr. A. F. G. KERR’s private herbarium. The author expresses his sincere thanks to all the gentlemen who made this revision possible.