Chromosomal Changes Observed in Natural Populations of Paris tetraphylla A. Gray

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Mitotic chromosomes of Paris tetraphylla (2n=10) in chilled condition were observed in metaphase of the plants belonging to seventeen groups gathered from six localities. The differential segments which manifest undercharging of nucleic acid in low temperature condition were found restrictedly at the distal region of the short arm of chromosome C. According to the patterns of this region, six different types were distin-guished as for this chromosome. Chromosome D was the only satellited chromosome among the complements of the genom of this plant. As for this chromosome two different types were distinguished according to the size of this satellite.
The chromosome composition of the plants of each of the seventeen groups was analyzed with respect to the types of chromosomes C and D. The results obtained are as follows; 1) In ten groups out of seventeen, the plants had chromosome C or D in heterozygous condition, and in the remaining six they have them in homozygous condition. 2) The chromosomal constitution differs not only from locality to locality but also, with four exceptions, from group to group. 3) All the individuals belonging to one and the same group have the identical chromosomal constitution.
Based on these results it was assumed that in the natural population of P. tetraphylla, vegetative apomixis takes place far more conspicuously than in that of Trillium kamtschaticum, which propagates almost exclusively by sexual reproduction.