Several ecological characteristics in tetraploid F_1 hybrids of snapdragon (2n=32), Antirrhinam majus, raised artificially had been studied from 1951 through 1960. The author also carried out some trials on the breeding features of these F_1 forms in order to make their intensive use to be practicable. Results obtained are summarized as follows: 1. On the flowering time of F_1 hybrids definite heterosis was uniformly obtained in the earliness of blooming. 2. A positive heterotic phenomenon in the plant height of F_1 hybrids could not be observed. However, on the number of leaves developed distinctive heterosis was observed in several F_1 hybrids. 3. The grade of fertility through cross-pollinations was somewhat lower than that through self-pollinations as well as diploid snapdragon, and mother strains showing higher fertility by selfing could produce higher yield of seeds. Though the seedfertility of 4x snapdragon usually showed low degree, their F_1 hybrids had, in general, a good yield of seeds. And 4x F_1 hybrids had higher regularity of mitosis as compared with their mother strains. From such results, the further progress of introducing superior 4x forms will become available by utilizing F_2 generations.