5. Partial sterility studies. One case with about 75% pollen abortion and a ring of 8 chromosomes (originated by x-ray treatment of a homozygous 5-7 interchange stock) was identified by Mr. Lazaro as involving chromosomes 1, 5, 6 and 7. In new data from crosses of normal × 75% sterile plants, the offspring included 75% sterile:semisterile:normal::273:71:181. Six different semisterile plants derived from the ring-of-8 were shown by him to have a single ring of 4 chromosomes one of which was number one, while in no case was number 6 involved.
A stock homozygous for the interchanges involved in the ring-of-8 (1-5-6-7) has been established.