Commelina benghalensis L and C. caroliniana Walter, two allied weedy species of the Commelinaceae vary in their breeding and meiotic systems. The former is predominantly auto- and the latter facultatively xenogamous. Meiotic system of C. caroliniana also provides for higher recombination index, characterized as it is by high chromosome number and higher chiasmata frequency: On the contrary C. benghalensis has fewer chromosomes and closed breeding system for which reason it generates little genetic variability. This difference qualifies C. benghalensis as a “specialist” and C. caroliniana as a “generalist”