Inheritance of Two Female‐Sterile Characters in Dwarf‐Internode Castor ( Ricinus communis L.) 1

Two female‐sterile characters in dwarf‐internode castor were investigated and the inheritance of each appeared to be controlled hy a single recessive gene. The symbols fs 1 and fs 2 are proposed. In fs 1 , all pistillate flowers failed to open, and pollen‐fertile staminate flowers tended to remain closed or only partially opened. Perianth segments in pistillate flowers were tightly fused. The epidermal cells of the perianth of flowers of both sexes were abnormally enlarged, resulting in a rough, pebble‐like surface. Normal‐monoecious plants had smooth epidermal layers. The perianths of the pistillate and staminate flowers were 25 and 40% thicker, respectively, in fs 1 than in the variety ‘Hale.’ In fs 2 , pistillate and staminate flowers appeared normal, but capsules failed to enlarge after stigmas were fully exserted. The stigmas dried within a few days, followed by gradual drying of the capsules. Pollen was fertile and stained easily. Cause of the fs 2 type female sterility was not apparent in this study.