At meiotic prophase of haploid maize, the number of microsporocytes forming 10 univalents or no bivalents, was found to be about 50 percent of the total 942 randomly selected cells. It was postulated that most of the duplicate factor inheritance, and perhaps also the triplicated and the quadruplicate factor inheritance in maize, are intrachromosomal.The frequent appearance of 10 univalents and the persistent chainconfigurations of the infrequently formed bivalents at diakinesis constitute a convincing evidence that modern maize is an alloploid with perhaps a basic chromosome number of five.The origin of spindle is discussed. The evidence that one or two strayed chromosomes were associated, at the centromeres, with an independent spindle at second meiotic metaphase, led to a conclusion that the spindle is of nuclear origin, probably in the centromeres of the chromosomes.
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Y. C. Ting (1966) studied this question.