A Cytological Analysis of Self-Sterility in Tradescantia

Abstract

1. Germinating pollen grains of Tradescantia are described as they appear in aceto-carmine smears of pollinated styles. 2. Many species of Tradescantia are self-sterile. 3. Compatible and incompatible pollination can be distinguished cytologically. The pollen grains germinate normally in the latter, but their growth is inhibited. 4. Cross-sterile pollinations cannot be distinguished quantitatively nor qualitatively from self-sterile pollinations. 5. Natural populations of diploid tradescantia can be divided into intra-sterile, inter-fertile classes on the basis of pollen tube behavior. 6. The number of these classes in natural populations is found to be large. 7. The main facts revealed by this purely cytological examination are in line with the oppositional factor hypothesis although there is disagreement on a few minor points.