Abstract: A method for producing genes conferring resistance to herbicides, growth regulators or other chemical agents in vascular plants is disclosed. Mutagenized spores of ferns of the genus Ceratopteris are grown in the presence of a herbicide, growth regulator, or other chemical agent and resistant mutant gametophytes are selected. Self-fertilization in the selected mutant gametophytes yields homozygous diploid sporophytes which also exhibit resistance. The sporophytes grown to maturity yield mutant spores having identical haploid genotypes which are grown to confirm the existence of resistance to the herbicide, growth regulator, or other chemical agent. The method produces vascular plant genes conferring resistance to the herbicide, growth regulator or other chemical agent.