Chromosome numbers for 9 tribes and 73 genera of Rutaceae are examined
for the probable chromosome base numbers in these taxa. There is abun
dant dysploidy and infrageneric polyploidy in the large Rutoideae/Todd
alioideae complex. We found that x = ls was typical for the tribes Zan
thoxyleae and Toddalieae; probably ancestral in the Boronieae and perh
aps in the Ruteae, Diosmieae, and Cusparieae; and characteristic of su
bfamily Flindersioideae. Considering the basic position of elements of
Zanthoxyleae and Toddalieae in the family it appears that diploid x =
18 is ancestral in the Rutaceae. The morphologically advanced Citroid
eae are invariant for x = 9 and may be a product of dysploid reduction
.