抄録
1. Irregular behavior of chromosomes, was not found in the meiosis of sterile hybrids ; sexual organs such as ovary and anther were also anatomically normal. 2. During the development of megaspore in sterile hybrids, deterioration, possibl.y in a larger pairt due to the suppression or failure of nuclear division, was found to occur at various stages covering from the first division of the innermost cell of the tetrad until the maturation of embryosac.At the time of heading, there were found, besides normal embryosacs, several kinds of abnormal ones which were varying from those showing only a trace of embryosac cavity to those containing a number of nuclei. 3. Failure of the development of microspore was found to advance after the "second colo-tracting stage" (according to KIHARA'S nomenclature), possibly with the first and second divisions of pollen nucleus. At the time of heading, pollen grains seemed to be classified into three types as (A) normal pollen containing three nuclei, (B) abnormal pollen containing two nuclei, poor in starch content an-d smaller in diameter, and -(C) innert pollen corl.tail.ing one nucieus and irregular in shape. 4. Considering from the above mentioned facts and other phenomena such that ncrmal pollen percentage depends upon the combination of parental varieties and is not dirferent between reciprocal crosses(as reported in the 2nd article of this series), the degenera.tion of gametes in sterile hybrids seems to be due to certain gene conrbinations which might be 'produced by the recombination in meiosis and carried by those gametes themselves. It was assumed as a working hypothesis that a genetial factor, X, w, hich act within germ cells to maintain the normal development, would be duplicated, and thus intervarietal hybrid Xlx2 xxlX2 would be semi-sterile owingto the degeneration of xlx2 gametes. 5. As a first step of gene analysis, two nearly related varieties, 219 (non-glutinous) and 221 (glutinous), and the third variety, 63 (gluti-nous), among thern 219 x 563 was semi-sterile while 221 x563 and 219x221 were free from sterility, were taken as materials, and variety 563 was crossed with the pdllen of Fl and F2s of219 X 221 .
