4. In a field corn test in 1938, 311 different hybrids and inbreds were grown. A total of 14,916 ears were picked and of this number 2 (from 22 different lines) were classified as semi-sterile. This is not a good determination of the frequency of changes giving semi-sterility, but is an indication of the types of changes that occur. Progeny of 24 of the 26 ears have been grown for one to three generations to test the transmissibility of these sterilities. Twelve were definitely transmitted, three had questionable transmission and nine were not transmitted and were probably due to environmental or physiological causes. Nine of the twelve have been examined cytologically, and in these the following changes were found: asynapsis, a 1-6 translocation, a 6-8 translocation, a pollen lethal character with no apparent chromosomal change or deficiency, and a long inversion in chromosome 1 including the centromere. It is of particular interest that the inversion in chromosome 1 was found in three different hybrids having as one parent, the inbred U.S. 4-8. It would be desirable to know if 4-8 has been found to have this inversion in the heterozygous condition and whether any unusual number of semi-sterile ears have been found in hybrids with 4-8. The 4-8 inbred used in the hybrids grown in Connecticut was not homozygous for the inversion since all the ears were not semi-sterile. It could have been obtained by contamination, but it seems unlikely that three hybrids with one parent in common would have been so affected. The inversions are apparently the same cytologically although crosses between them have not been made as yet to detect any differences.
Twelve semi-sterile ears, obtained from other field corn tests and sweet corn trials, have been tested for transmissibility. Five were not transmitted, one possibly is transmitted and six were transmitted. From the last six a lethal ovule character was found, a 2-5 translocation and a 6-9 translocation. Three have not been examined cytologically.