Studies on Self-Sterility VII. Heredity and Selective Pollen-Tube Growth.

A new genetic interpretation of self-sterility as manifested in Sicotiana alata Lk. and Otto var. grandijiora Comes and Sicotiana forgetiana Hort. (Sand.), or their hybrids, has been proposed recently (EAST and M ~ N G E L S DORF 192.5). The detailed evidence on which this interpretation rests i< given in the present paper. Self-sterility appears to behave as a simple recessive when the,e specie< are crossed with the self-fertile species, Nicotiana Langsdorgi i L. Their interaction is thus similar to that found by COMPTON (1912) in crosses between self-fertile and self-sterile strains of Resedu odorafa L. The strains of Nicotiana homozygous for self-sterility behave a 5 if their peculiar condition mere controlled by several hereditary factors. Like combinations of factors produce like groups of plants in so far as their compatibility with each other is concerned, just as like factorial combinations which lie a t the basis of morphological difl'erences produce groups which are alike in those characters. Generally speaking, all members of a given self-sterility group are cross-sterile uith each other reciprocally, but are cros5-fertile with the members of every other group. These distinctions in compatibility are due to hereditarily controlled reactions of such a nature that some pollen-tubes (compatible matings) show a rapidly accelerated rate of growth which permits fertilization in from three to live days,-depending mainly on the temperature, while other pollen-tubes (incompatible matings) show a slower and more nearly uniform rate of growth which ordinarily does not allow the generative nucleus to reach the micropyle before the flower withers and falls.