Abstract
A detailed analysis of the karyotype and the meiotic behavior of the South American endemic Lathyrus hasslerianus is provided in this study. The karyotype obtained is the most asymmetrical of section Notolathyrus, which together with the particular morphological characters and ecological requirements supports a derived state of this species. Meiotic analysis showed the occurrence of univalents and out of plate bivalents in metaphase I, which ultimately leads to the formation of micromicrospores or micronuclei at the sporad stage. Mechanisms of aberrant sporad formation are discussed. Even though, pollen viability was reduced, it does not compromise the species fertility as shown by the analysis of the seed set.
