This extensive collection, famous among algologists both of the Old and the New World, forms part of the collections of the National Herbarium (Rijksherbarium) Leiden since 1934. About fifty years ago it was started by Mrs. Dr. A. A. WEBER-VAN BOSSE (1852—hodie), an enthusiastic pupil of HUGO DE VRIES. The colonies of Nostoc, living in the ditches round about the Dutch village of Doom, evoked her admiration, which was the primary cause of an intense study in the freshwater as well as in the marine Algae. In the harbour of Den Helder North Sea Algae were collected; by collecting Algae on trips to the French Atlantic Coasts and several times to Norway (1883—1885) and further on a South African journey (1894—1895) the herbarium grew, as it did by the Malaysian specimens collected in Java, Celebes, etc. (1888—1889). During this Malaysian tour Mrs. WEBER worked in Tjibodas, where she described the new genus Phytophysa. In Sumatra (West Coast, Lake of Manindjau) she discovered in collaboration with her husband, MAX WEBER, a new case of symbiosis between Algae and Sponges.