Morphogenesis of the Stamenless‐2 Mutant in Tomato. I. Comparative Description of the Flowers and Ontogeny of Stamens in the Normal and Mutant Plants

The single gene recessive mutant stamenless‐2 (sl 2 /sl 2 ) differs phenotypically from the normal (+/+) only in the stamen structure. Stamens of the mutant plants were laterally free, twisted, shorter, paler in color, possessed abnormal pollen, and bore naked external ovules (E.O.) on the adaxial surface near the junction of anther and filament. Mutant plants grown in the field during summer produced flowers in which a number of carpel‐like organs (‘carpelloid stamens‘) with few or no E.O. replaced the stamens. On the other hand, plants grown in the greenhouse during winter possessed flowers with greater number of yellow and pubescent stamens and many E.O. Study of stamen ontogeny revealed that at initiation (up to 100 μ in length) stamen primordia of normal and mutant plants resembled each other. Thereafter the development of stamens in the two genotypes could be distinguished.