Reciprocal crosses were made between H. cannabinus (2n=36) and H. radiatus (2n=72). An F1 plant was obtained only when H. cannabinus was used as the female parent. The F1 plant grew vigorously and was totally sterile. In pollen mother cells, 18II + 18I was most freguently observed. Judging from these results, the tetraploid species, H. radiatus, contains one genome which is homologous with that of H. cannabinus and another genome which is not.

H. cannabinus (2n=36)とH. radiatus (2n=72)との相反交雑では、前者を母親にした場合のみ、交雑が成功した。F1は著しく雑種強勢を示したが、完全に不稔であった。F1植物の体細胞の染色体数は2n=54で、成熟分裂では大部分の細胞が18II+18Iを示した。したがって、H. radiatusには、H. cannabinusと相同のゲノム1つと、全く非相同のゲノム1つを有すると推定した。