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Absolute length measurements are reported for all chromosomes of 271 pachytene microsporocytes from 89 anthers of 31 related corn plants. Arm ratios are reported for all of these chromosomes where it was possible to locate the centromere. Data are compared to previously published measurements of corn chromosomes. Sample variances and coefficients of variation of chromosome lengths and arm ratios are compared. The results include findings that longer chromosome arms have greater variances but smaller coefficients of variability and that chromosomes with larger arm ratios have inherently more variable arm ratios. These greater variabilities in arm ratio were not correlated with corresponding greater variabilities in length of the chromosomes involved. All results are consistent with the interpretation that the chromosomes have two kinds of variability: one which seems to contribute approximately uniformly per unit length to variability throughout the genome while the other kind of variability may be a characteristic property of each chromosome unrelated to length in any consistent way. Chromosome knobs do not appear to influence variability in length of chromosome arms in which they occur. Tripsacum chromosome material does not appear to differ in its length variability from corresponding corn chromosome material for which it has been substituted.

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