In the present study, meiotic chromosome numbers and meiotic behaviour of six populations belonging to four species growing in Iran, namely Paracaryum modestum (2n = 2x = 24), Paracaryum persicum subsp. macrocarpum (2n = 2x = 24), Paracaryum undulatum (2n = 2x = 24) and Paracaryum rugulosum (2n = 2x = 24) were determined. All chromosome counts are consistent with a proposed base number of x = 12. In addition, we report here the chromosome counts of P. modestum and P. undulatum for the first time. Almost all taxa studied here displayed regular bivalent pairing and chromosome segregation at meiosis. However, meiotic abnormalities observed included varied degree of fragmented chromosomes, laggards and bridge in anaphase I to telophase II, precocious division of centromeres, asynchronous nucleus, binucleus and cytomixis. We found a striking association between meiotic behaviour and habit morphology. In addition, P. modestum was originally described as a member of Paracaryum but was excluded from this genus and treated as Mattiastrum. However, this species is clearly similar to P. rugulosum and P. persicum and is treated here as a Paracaryum.
