The karyotype ofZ. pendulavar.quadricolor(2n23,n.f.= 28) is shown to have 6M + 7A+10T chromosomes. This variety is suggested to have evolved from Z.pendula, having 4M+8A+12T chromosomes, by two simultaneous centric fusions, involving two T chromosomes, the satellited A chromosome and another A chromosome, resulting in the two additional M chromosomes and the newly formed satellited A chromosome ofZ. pendulavar.quadricolor.The satellited A chromosome of the variety is suggested to have been formed from the short arms of the two A chromosomes ofZ. pendula.