Karpechenko (1928): "Closely allied species are often known to possess numbers of chromosomes which are related to each other as common multiples. In the genus Chrysanthemum, for instance, there occur species with 18, 36, 54, 72, and 90 chromosomes....in Rumex....species with 20, 40, 60, 80, 100 and 200 chromosomes.....There exists an opinion that the occurence of such relations is due to hybridisation, that polyploid multichromosome species originate from intercrosses between species with a small number of chromosomes."