1. 温湯法による集団除精法を種々の作物に適用する際に, 供試花の成熟程度によつて花粉の熱に対する抵抗力に差がある様に思われる。此の点を明らかにする為に, 水稲品種「千本旭」を用いて幼穂並に花粉の成熟過程の観察と, その種々なる時期に於ける温湯処理が, 花粉及び雌蕊の機能に対し如何なる影響を及ぼすかを調査した。2. 処理条件は, 低温区40℃-8分, 標準区43℃-8分, 高温区46℃-8分の3区とし, 処理時期を, 通常処理期, 出穂期, 出穂前3∿5日, 7∿8日, 11∿13日の5期とし, 両者を組合せて15試験区を設けた。3. 出穂期以前の処理により, 供試穂の出穂期に変動を来さしめなかつたので, 出穂前日数の決定は, 処理がその穂の出穂期に先立つ日数を以つてした。4. 花粉の成熟状態は, 出穂前11∿13日では花粉母細胞のMeiosis, 7∿9日では花粉の外殻形成期, 3∿5日は花粉内容の充実期であり, 出穂期以降に於いては花粉粒はすべて完成していた。5. 温湯処理後直ちに袋掛けを行い, 自家結実の状態によつて花粉の機能を調査し, 一方Clipping methodによる結実率によつて雌蕊の機能を調査した。更に結実種子の発芽試験を行い, 之等に対する処理の影響を考察した。6. 花粉の熱に対する抵抗力は, 成熟過程にあるものは一般に強く, 出穂期に於いて著しく弱まり, 開花直前の成熟花粉が最も弱かつた。又出穂期以降に於ける雌蕊の熱に対する抵抗力は, 花粉のそれに比して著しく強いものと思われる。7. 結実種子の発芽は, 最適処理条件区のものが最も良好であつたが, 処理, 時期による差は認められなかつた。8. 以上の結果より, 温湯法により集団除精を行うに際しては, 処理に先つて開花直前の成熟程度均一なる頴花を選び, 未熟花はつとめて摘除する必要のあることが判明した。1. The present paper deals with the results of investigations on the observation of growing stages of immature panicle and pollen grain of rice variety "SENBON-ASAHI" and on the effect of hot water treatments in several times of these stages upon the function of pollen and ovule. 2. In this tests, 3 conditions of hot water treatment were adopted, that is low (40℃ for 8 minutes), standard (43℃ for 8 minutes) and high (46℃ for 8 minutes) temperatere section. These treatments were carried out on 5 different stages namely optimum time of treatment, heading date, 3 to 5 days before heading, 7 to 9 days before heading and 11 to 13 days before heading. 3. Heading date of treated panicle was unchanged owing to the treatment before heading, for this reason "days before heading" was determined by the number of days preceding the heading date of treated panicle. 4. The aspect of growing pollen was observed as follows : Meiosis of pollen mother cell was found in 11 to 13 days before heading, outer hull of pollen was formed in 7 to 9 days before heading, protoprasm of pollen was incresing in 3 to 5 days before heading and all pollen grains were complete after heading date. 5. Pollen function was tested by the fertility of treated panicles pollinated with treated pollen and ovule function was by the fertility of treated panicles pollinated with normal pollen by clipping method. 6. About the heat resistance of pollen, pollen in growing stages was generally stronger than complete pollen and especially the pollen just before the flowering was most inferor. It was considered that heat resistance of ovule was very strong as compared with the pollen after heading. 7. The germination of seeds which raised under the optimum time of treatment were best of all, but no evident tendency due to different conditions and stages of treatment was recognized in germination of seed. 8. According to these results, it was identified that we must select uniform florets on degree of maturity and must remove immature florets in treated panicle as much as possible
