The medium defined by Nitsch was used in the production of haploid plants of various species of Nicotiana raised from pollen grains. In this procedure, pollen that were still uninucleate were isolated and then cultured in vitro. Some pollen grains proliferate into embryo-like structures that develop in stages similar to those of zygotic embryos. The plantlets matured and flowered profusely, but did not set seed.