Chromosome numbers in Argentinean Acanthaceae

Mitotic and meiotic chromosome numbers are reported for 22 species representing eight genera of Argentinean Acanthaceae. Counts for 18 of these species are published for the first time (including the first count for the genus Chaetothylax, 2n = 28). In Siphonoglossa, 2n = 36 is a newly reported chromosome number and n = 13 is a new number for Stenandrium. Polyploidy and aneuploidy have been important in chromosomal evolution of Acanthaceae and diploids are apparently not very common. The basic number X = 7 seems to be primitive for the family, from which the widespread X = 14 would have been derived