Previously, the chromosome numbers of some species of Loganiaceae were dealt with (Gadella, 1961, 1962, 1963). The chromosome numbers of 7 species are reported in this paper, of which 4 species, all belonging to the genus Strychnos, had not been investigated cytologically before. The materials, kindly supplied to me by Dr. A. J. M. Leeuwenberg and by Ir. F. Breteler, were collected in the form of seed-samples in the Ivory Coast and in Cameroun. The plants of 2 species originate from botanical gardens. Living material of all species (except for Strychnos lernata Gilg. ex Lwb.) is grown in the botanical garden of Wageningen (WAG). The determination of the chromosome numbers was based on the study of roottipmitoses. Roottips of the plants were fixed in Karpechenko, embedded in paraffin, sectioned at 15 micron and stained according to Heidenhain’s haematoxylin method. The results may be summarized as follows: 1. Nuxia floribunda Benth.: 2n = 38 Origin of the material: S. Africa, obtained from the University of Stellenbosch. Seeds probably collected in the wild. Herbarium material of the mother-plant: J. J. Bos, no. 310 (WAG). Herbarium material of seedling: A. J. M. Leeuwenberg no. 3665 (WAG). References: Gadella (1963): 2n = 38. 2. Strychnos dinklagei Gilg.: 2n = 44 Origin of the material: Ivory Coast, Forêt d’Abouabou, between Abidjan and Grand Bassam. Herbarium material of the mother-plant: R. A. A. Oldeman no. 845 (WAG). Herbarium material of the seedling: A. J. M. Leeuwenberg no. 3561 (WAG). References: Gadella (1963); 2n = 44. 3. Strychnos innocua Del. subsp. innocua: 2n = 44 Origin of the material: Ivory Coast, 16 km S. of Ferkéssédougou. Herbarium material of the mother-plant: A. J. M. Leeuwenberg no. 4435 (ABI, WAG). 4. Strychnos millepunctata Leeuwenberg: 2n= 441) Origin of the material: Ivory Coast, Forêt d’Abouabou, between Abidjan and Grand Bassam. Herbarium material of the mother-plant: J. J. F. E. de Wilde & A. J. M. Leeuwenberg no. 3447 (ABI, WAG). 5. Strychnos samba Duvign.: 2n = 44 Origin of the material: Cameroun, 4 km S. of Nguélémendouka. Herbarium material of the mother-plant: F. J. Breteler no. 2051 (WAG). 6. Strychnos spinosa Lam.: 2n = 44 Origin of the material: obtained from the botanical garden of Groningen, the Netherlands, origin unknown. Herbarium material of cutting: A. J. M. Leeuwenberg no. 3564 (WAG). References: Mangenot and Mangenot (1958): 2n = 44. Miège (1960): 2n = 44. Gadella (1962): 2n = 44. 7. Strychnos ternata Gilg. ex Leeuwenberg: 2n = 44 1) Origin of the material: Cameroun, 27 km from Bertoua on road to Bétaré Oya. Herbarium material of the mother-plant: F. J. Breteler no. 2196 (WAG). Herbarium material of the seedling: F. J. Breteler no. 2994 (WAG). Twenty-one species of the genus Strychnos have been studied up to the present. The following chromosome numbers have been counted: 2n = 24 (3 species, counted by Mohrbutter, 1936); 2n = 44 (16 species); 2n = 88 (2 species). From these data the conclusion may be drawn that the more common basic number of the genus Strychnos is X = 11 or 1 = 22.