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We analyzed germination percentages and germination rates at four temperature treatments (5/15, 10/20, 15/25 and 20/35 degrees C) and in light or darkness in four endemic species of the genus Gymnocalycium with different flowering phenologies from the Cordoba Mountains (Argentina). Gymnocalycium bruchii flowered and dispersed its seeds very early in the season in comparison to the other three species. No seeds germinated in darkness or at the coldest temperature regime. For all species except G. bruchii, germination was higher at the two warmest treatments. Gymnocalycium bruchii germination was maximum at the second warmest temperature (15/25 degrees C) and did not germinate at all at the highest temperature treatment (20/35 degrees C). Germination varied strongly among species, from about 80% in G. quehliaum to 20% in G. monvillei. Germination rate (t(50)) varied more strongly among temperature treatments (from 15 to 7 days in the coldest and warmest treatments respectively) than among species. The lack of germination of G. bruchii at 20-35 degrees C could be related to its early flowering phenology.