Abstract
Three artificially induced tetraploid flowers were created by seed treatment with colchicine solution in 1950-1951. (1) Coral flower is a kind of garden annuals. It has a peculiar habit of flowering, that is, small five pink petals of each floret open slowly in the twilight of evening and soon fade till darkness of night comes. The name maybe refers to bearing a plenty of small coral colored fruit-pods on the stems. Tetraploid coral flower grows vigorously with longer stems, larger leaves and much enlarged florets, furthermore, having longer flower season due to lowered seed fertility than diploid. (2) Viscaria is a well-known biennial garden plant like Pinks. Tetraploid one grows rather slowly at the young stage in winter and then becomes more vigorously and higher-habited in warm spring, producing so enlarged flowers but fewer seeds than diploid. (3) Edging lobelia is a pretty deep-violet flowered garden ribbon plant. Especially, Crystal Palace which was used for the trial is a good compact-habited variety. The tetraploid plant produced by chromosomal doubling was much dwarfened and had thicker leaves, bearing the same flowers as large as diploid. This plant was sterile completely and damaged severely to death by winter cold. It is presumed that such“polyploid feebleness”as the above lobelia is possibly caused by surplus duplication of the genetically similar chromosomes which are affecting plant growth respectively.
