The value of the great Historic Herbaria of the World – among which the Classical Rijksherbarium at Leyden, founded by BLUME, occupies a position of the first importance – seems scarcely to need emphasis in these days, when Botanists, working along so many different lines, find the collections stored in them so essential for the prosecution of their researches. When these collections were originally inaugurated they were intended to be mainly a „Hortus siccus”, a depositary of dried specimens representing the vegetation of a particular country or continent. With the widening of outlook, however, the connection of the flora of one region with that of another came to be recognised, and in the larger centres of botanical activity a Herbarium was gradually built up containing, as far as might be possible, collections representative of the vegetation of the world. With the aid of these collections the great „Floras” of the different regions of the World have been written, and from Holland, as from other countries, have emanated many early works of great importance to the Systematic Botanist and to the student of Plant Geography. Without these authentic records, as exemplified by the specimens which are the types of the scientific descriptions, the work of the Taxonomist would be of as little value as would be that of the Historian without the tabulated evidence contained in the actual historical documents.