Chromosome Numbers of the Family Cruciferae. I

Chromosome numbers are given for 69 collections of 24 species of Cruciferae in the genera Alyssum, Arabidopsis, Arabis, Barbarea, Cakile, Eutrema, Hali-molobos, Nasturtium, Rorippa, Thellungiella, and Turritis. The following chromosome numbers are reported for the first time: Alyssum desertorum, n = 16; Arabis canadensis, 2n = 14; A. divaricarpa, 2n = 13 + 2B, 14, 20 + 2B, 21, 28; A. drummondii, 2n = 20; A. holboellii, 2n = 13 + 2B, 20 + 2B; A. lemmonii, 2n = 14; A. lyallii, 2n = 21; A. lyrata, 2n = 32; A. pendulocarpa, 2n = 14; Barbarea orthoceras, 2n = 16; Cakile edentula, 2n = 18; Rorippa curvisiliqua, 2n = 16; Thellungiella salsuginea, 2n = 14. It is concluded that species of Arabis native to North America and western Greenland have the base number x = 7 and many of them are apomictic whereas Eurasiatic species of this genus have an x = 8 base number and are sexual.