1. Hibiscus mutabilis (フヨウ) に性の草本である H. meehanii を交配し, 花色の異なつた6系統の木本性 F1 植物を育成した (第1, 2, 3表). これらをさし木によつて増殖し, その開花期を両親と比較した.
2. フヨウは9月に咲き始め, 10月に開花を終了するが, meehanii は7月に咲き始め, 9月中に大部分が咲き終わる. 育成したの開花期は, 7月から始まつて11月におよび, 両親の開花期を合わせたよりも長かつた(第4, 5表; 第1, 2図).
の開花総数は, 両親の平均よりも多かつたが, フヨウよりも多いのは1系統だけであつた.
3. 新しく導入した H. para mutabilis (ロザンフヨウ), H. sinosyriacus (タイリンムクゲ) の両種は, ともに6月から開花し, 7月にその大半が咲き終わり, 開花の季節的消長のパターンは, フヨウよりもムクゲのそれに近かつた (第6表; 第3図).

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The purpose of this study was to find the most promising F₁ hybrids by crossing several self-incompatible strains of induced pseudogamy in Matsushima No. 2 and Chiba No. 1 chinese cabbage.
The authors obtained 48 F₁ hybrids by crossing 23 self-incompatible strains. The seeds of these F₁ hybrids were sown on the two different dates. The hybrid vigor and the various characteristics which appeared in these F₁ hybrids, were observed.
(1) In crossing these self-incompatible strains, hybrid vigor was affected by different cross-combi-nations and different sowing dates, and especially the total weight, head weight etc. were increas-ed by hybridization.
(2) The rate of increase in F₁ hybrid yield was greater than that of their parents, in both early and late sowing, and the variation in their yield was greater than those of other characteristics. It is thus possible to find a fairly productive F₁ hybrid.
(3) Generally, the degree of hybrid vigor which appeared in early maturity and leaf number was less in comparison with those of other charac-teristics. However, a few of these cross-combi-nation showed marked vigor in early maturity and leaf number characteristics. Therefore, it was possible to select the hybrids that matured earlier, and had more leaves per head than Matsushima No. 2.
(4) There was correlation between a superior parent yield, an average yield of parents and F₁ hybrid yield, respectively, but no correlation be-tween an inferior parent yield and F₁ hybrid yield. The F₁ hybrid resulting from crossing productive parents showed increased vigor, when their parents were homozygous.
(5) In general, F₁ hybrids resulting from the crossing of these self-incompatible strains did not have more excellent characteristics than those of standared variety, Matsushima No. 2. However, some of these F₁ hybrids seemed markedly promising. Finally, we selected 6 F₁ hybrids that had showed adaptability to early sowing and late sowing, which were superior in early maturity, yield, uniformity and disease-resistance (soft rot) to Matsushima No. 2.

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1. 新しい観賞植物育成の目的でおこなつているHibiscus の交配実験のうち, 東アジア原産の4種の木本植物と, 北米原産の6種の宿根性植物との相互交配をおこなつた。
2. 種内交配では, フヨウおよび北米群のすべての種は自殖でよく着さくし, 充実した多数の種子を得 (Table3), その発芽率も良好であつた (Table 6)。
東アジア群ではフヨウを除き, 自殖では全く着さくしないか, さく果ができても充実した種子をえられなかつた (Table 3)。
3. 北米群内での6種の種間相互交配は高率で着さくし (Table 4), 充実した種子多数を得 (Table 5), また種子の発芽も良好であつた (Table 6)。
東アジア群内の種間交配では, フヨウを除き, 相互に着さくするがやや低率であり(Table 4), 少数の充実した種子を得 (Table 5), 種子の発芽も正常であつたがやや低率であつた (Table 6)。
フヨウとほかの3種は同じ東アジア群であつても, 相互交配で種子はえられなかつた (Table 5)。
フヨウと北米群間の種間交配では, フヨウを母本とした時はすべて成功したが, その着さく率, 種子数, 発芽率などは, 北米群内の種間交配に比べて低かつた (Table4～6)。
北米群を母本としてフヨウを交配した場合はすべて不成功であつた (Table 7)。

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