Meiotic Chromosome Behavior in Species, Species Hybrids, Haploids, and Induced Polyploids of Gossypium.

HE genus Gossypium, a member of the Malvaceae, includes the T species of cultivated cottons. More than IOO species of Gossypium have been described, but recent workers include all the described types in fewer than 20 species (HUTCHINSON and GHOSE 1937; HARLAND 1939). The basic chromosome number in the genus is 13, and all species studied have either 13 or 26 pairs of chromosomes. The cytological behavior of all species hybrids, except one, included in this paper has been reported previously by other workers. Further data on the meiotic chromosome behavior of species hybrids and haploids are given, together with a review of published data. Data on the meiotic chromosome behavior of several induced polyploids of Gossypium are given for the first time. In the present work emphasis is placed upon data relative to the amount of structural differences among chromosomes of different species and to the meiotic chromosome behavior of polyploids. These data are used in an attempt to define more accurately the relationships of Gossypium species and to make clearer the process of speciation of the genus.