Josephson and Jenkins (Jour. Amer. Soc. Agron. 40:) have shown that partial male sterility occurs in hybrids in which the inbred Ind. 33‑16 is used on the female side of the cross. An analysis of the degree of pollen abortion in single cross combinations, involving 33‑16, Ky27, H21 and C.I. 61, confirms the results of Josephson and Jenkins. Single crosses in which 33‑16 was used as a seed parent produced an average of 46% aborted pollen, with considerable variation in the degree of sterility between plants. Crosses in which 33‑16 was used as a male parent produced only normal pollen. Pollen abortion, but to a lesser degree (approximtely 25%), was observed in crosses involving Ky27 as a female. Fertile and partially sterile plants were examined cytologically to determine whether or not the cytoplasmic male sterile condition was associated with abnormal chromosome behavior during microsporogenesis. Meiosis was normal in all plants examined. Pollen, in most cases, seems to degenerate prior to the first pollen grain mitosis.

In addition to this material, five cytoplasmic male sterile yellow single crosses supplied by Dr. D. F. Jones were also studied cytologically. Abortive pollen in these crosses ranged from 75 to 100%. As was true in the case of the white hybrids, microsporogenesis was normal in this material, including those plants that produced 100% abortive pollen at anthesis. This condition appears to be similar cytologically to that of several completely or partially sterile species hybrids.

William L. Brown and

Mary Ann Coyle