On the relationship between the polyploidy and the occurrence of pollen-grains with an increased number of germinal apertures in the tribe Brassiceae

The authors\u27 examinations on the number of germinal apertures of pollen-grains in the tribe Brassiceae have disclosed the following facts : 1. As shown in Table 1, the number of germinal apertures is 3 in each of pollen-grains in the diploid forms, mainly 3 and in part 4 in tetraploid ones, and predominantly 4 and in a far small proportion 3 or 5 in hexaploid ones. 2. Frequency occurrence of the anomalous pollen-grains with supernumerary apertures in some polyploid forms showed certain variation among different anthers within the same flower (Table 2). 3. It was safely asserted, irrespective of the foregoing irregularities, that the germinal apertures in pollen-grains of certain polyploidy forms tend to increase in their number in accordance with the degree of polyploidy of those forms concerned; and, moreover, the occurrence of 4-apertured pollen-grains becomes to be much frequent in the autotetraploid forms as compared with the allotetraploid ones. The latter fact is very interesting to show that there exist certain definite difference between the polyploid forms of different nature of ploidy. 4. The frequent occurrence of pollen-grains with the supernumerary germinal apertures in the polyploid plant may be ascribable to certain irregularities of meiotic divisions and of the subsequent processes in microsporogenesis, but the causal mechanism remains unidentified