During his zoological collecting trips to the Antilles Dr. P. Wagenaar Hummelinck also gathered several samples of fresh and brackish water algae, which have been presented to the Rijksherbarium, Leiden. The present paper deals with the Chlorophyta of that collection, with the exception of Enteromorpha. Wagenaar Hummelinck’s localities 1936—1949 have been described in the “Studies on the Fauna of Curaçao”, Vols. 1 (1940), 2 (1940) and 4 (1953). Sta. 76 A has been illustrated in Vol. 1, Plate Vb; Sta. 97 in Vol. 2, Plate IV a; Sta. 500, 382, 63 and 678 in Vol. 4, Plates Ib, IIa, IIb and Va, respectively. The 1955 localities will be described in a “Third List of Localities”, to be published in a forthcoming volume of this series.