Abstract
1. In the tetraploid Allium odorum (n=2x=16), the variations of chromosome number were observed in meiosis in spontaneous as well as artificial conditions. The chromosome number series of n=9, 11 to 19, 31, and 32 were counted in the first pollen mitosis.
2. The chromosome numbers in pollen mitosis are distributed almost equally on both sides of n=16 in the spontaneous variation, but in the artificially intensified condition, both at both the lower and higher temperature, the frequency in each chromosome number decreases on the side of n_??_16, consequently the percentages on the other side of lower complements increase (Fig. 3).
3. The observed frequency in each group of the chromosome numbers 16-16, 17-15, 18-14, 19-13, 20-12, agrees well with that calculated by method of POISSON distribution.
4. A pair of satellited chromosomes was found at the normal metaphase plate in the pollen mitosis of this phylogenetically autotetraploid plant. They are distributed equally as other complements in pollen grains.
