Cucurbita-crosses. XV. Flower pollination at 4 a. m. in the production of C. pepo × C. moschata F1 hybrids.

In the species crosses of C. papo var. "Nishikikanro" as pistillate parents, cross-com-patibility of C. Ieeaxileea as a staminate parent is the highest in bud pollination at 7 a. m. of the day before anthesis (Cucurbita-crosses. XIII). As in the present articles, the results of crosses of C. pepo × C. moschata at different timcs demonstrate that only 4 a. m., crosses succeeded in the production of F1 plant.s. This may be due to high degree of both receptivity of C, papo and fertilization power of C. moschata. F1 hybrids were self-fertile and could be back-crossed to the parental species. The chromosome configuration at MI is 0.05 Iv+19.50 II+0.40 I per PMC. Seventy-three percent plates at MII receive a balanced number of chromosomes. Normal tetrads were 86.8% and fertile pollen grains, were 79.0% The characteristics of F1 plants were intermediate between those of their two parental species.