Tetraploid non-branching stocks which were induced by colchicine treatment usually produce a small number of double flowering plants in addition to the greater part of single ones, so that they are not suitable yet for economical growing to get cut-flowers. Besides, the tetraploid double flowering spikes are rather short, harder and later growing than diploids, although each florets is somewhat larger and possessed of numerous thicker petals. As doubiness of florets in normal diploid stocks is presumed to be arised from a monogenic recessive factor, namely, the double flowering plant is“ss”and the single one“Ss”, the original tetraploid single flowering plant is manifested with“SSss”and they produce numerous single flowering progenies included with three genic types, SSSs, SSss and Ssss, added with a few double flowering ssss-plants.<br>SSSs-typed plants have somewhat narrow and deep-greenish colored linear leaves, slowly growing habit and produce only single flowering plants. SSss-plants have the same habit as an original mother plant with wide leaves slightly serrated and bring forth only a few (2-16) percentage of double flowering plants in the next generation. Ssss-plants grow occasionally fast with fairly serrated wide leaves and are endowed with many“semi-double”florets which are formed with a few defective surplus petals, and, furthermore, they bear some times a smaller quantity of seeds than SSss-plants and give 23 to 28 percentage of double flowering plants in the next generation. Full double flowering ssss-plants which are completely sterile due to lacking in stamens and pistils are easily distinguished from single flowering by their strongly serrated larger ruffled leaves which are so brittle and much light-greenish colored. And here is a noticeable occurrence, that is, occasional appearance of the full double flowering plants in the progenies of Ssss or SSss-typed parents. They have the same deep-greenish colored and fairly serrated leaves and stout stems as sirlgle flowering Ssss-plants. These abnormal plants are possibly endowed with Ssss-factors but produce full double florets without stamens and pistils caused by unstable overwhelming of three recessive factors sss against one dominant S.<br>In order to raise percentage of double flowering plants in tetraploids (at least above 25%), Ssss-typed plants only should be ensured for seed production by morphological selection as mentioned above, because, on the contrary, SSss and SSSs-plants are usually superior in number in mass growing and are acting on lowering percentage of double flowering plants (less than 5%). The author expected theoretically, it would be easy to get fifty percent double flowering strains of triploid stocks which would be induced by crossing Ssss-typed tetraploid and Ss-diploid. However, so far as his experience concerned for three years, triploid seeds were hardly produced by the above crossing. Only two seeds were obtained in 1999 from 540 flowers cross-pollinated and they grew up well to a double flowering and a single flowering triploid plants. It will be worthy to note, however, that this triploid single F₁ plants obtained by crossing between a diploid branching purple-red and a tetraploid non-branching pink has produced many good F₂ seeds which are almost of the lavender-flowered tetraploid structure, and then each plant of F₂ or F₃ progenies are now becoming an initial of a new branching or non-branching tetraploid strain having white, pink, lavender or purple-colored flowers respectively. Although tetraploid stock strains are inferior to diploids in regard to get cut-flowers as stated before, they will be much useful and even precious for people who want to make researches in plant genetics.