The seed-morphology of the genus Notocactus (Schumann) Fric (sensu lato) was examined, and the genus divided into the following groups on the basis of seed-characters: IA. N. OTTONIS Group; IB. N. LINKII Group; II. N. CONCINNUS-N. SCOPA Group; IIIA. N. MAMMULOSUS Group; IIIB. N. UEBELMANNIANUS Group; IV. BRASILI-CACTUS Group; V. WIGGINSIA (Malacocarpus) Group; VI. ERIOCACTUS Group; VII. BRASILIPARODIA Group. A comparison with the seeds of the genus Parodia Speg. shows the close relationship of the two genera.