Intraspecific and interspecific consistency of karyotypes has been demonstrated for Pinus roxburghii and P. insularis. The complement of 24 chromosomes has been classified into five non-overlapping or distinguishable classes, a-e. Each class has been characterized by a chromosome length in angular scale and an arm ratio in logarithmic scale. Four satellited chromosomes have been identified. It has been proposed that the species examined in the genus Pinus are probably natural tetraploids of six basic chromosomes.
