Date of this Version
The wide-spread interest in the genetics of maize, coupled with the uncertainty as to the number of chromosomes occurring in this species prompted the investigation which is here reported. From a review of the literature it appears that Kuwada (1911, 1915, 1919) is the only worker who has reported extensive counts of maize chromosomes. His results are summarized in table 1. Variations were reported in the number of chromosomes both within and between varieties as well as between different cells of individual plants. He concluded that sweet varieties are usually characterized by having twelve chromosomes, and starchy varieties by having ten, as the haploid number. Several exceptions were recorded, as shown in the table. With one exception his sweet X starchy hybrids were considered as having a haploid number of ten chromosomes. The pollen mother cells of a single plant of Black Mexican had one univalent and eleven bivalent chromosomes, while cells of the root-tip had twenty-three chromosomes. He considered that this had been caused by non-disjunction. According to Kuwada's counts the haploid number varied as much as six chromosomes within some varieties. Since completing the investigation which follows, a brief paper has appeared by Longley (1924) concerning chromosome numbers in maize and related species. Four varieties including Chinese and Tepic maize are reported as each having a haploid number of 10 chromosomes.