An examination of embryonic development of 150 defective kernel mutants has revealed 15 lethal mutants that are blocked in their embryonic development at a stage prior to the formation of the first leaf primordium (only one of these mutants, E792, is described in the report by Neuffer and Sheridan in this issue). These mutants were examined early and late in kernel development by dissection of mutant kernels on self-pollinated segregating ears. There are nine mutants blocked at the proembryo stage and five of these are allelic. Four mutants are blocked in the transition stage and two mutants in the coleoptilar stage of embryo development. These stages are those defined by E. C. Abbe and O. L. Stein (1954). Since preliminary results indicate that eleven of the mutants are located on six different chromosome arms, it appears that several gene loci can result in stage-specific blocks in embryogenesis. Additional details on these mutants are reported in Sheridan and Neuffer (1981, to be published in the 39th Annual Symposium of the Society for Developmental Biology, S. Subtelny, editor).

William F. Sheridan and M. G. Neuffer