1. SevenCrocus species collected in natural habitats have been examined for chromosome numbers, three of them for the first time. 2. An up-to-date list of 80Crocus species arranged in taxonomic groups (divisions, sections), according toMaw, is given as an addendum, and the available chromosome numbers are cited. 3. The variation of chromosome numbers inCrocus is discussed. It is stressed that the pattern of variation in DivisionNudiflori differs from that of DivisionInvolucrati (Fig. 3). 4. Geographical distribution of chromosome numbers in each of the two divisions (Fig. 4) shows that theInvolucrati prevail in the western part of the area ofCrocus (districts A-B-C of the Map, fig. 5) and possess higher chromosome numbers than theNudiflori which are concentrated in the eastern part of the area (districts C-D-E) and whose chromosome numbers are lower on the whole. 5. Some ideas on the possible chromosome evolution inCrocus are presented tentatively.