Development of Androgenic Haploids - Under normal conditions the microspores mature into pollen grains in situ but in culture their morphogenesis is altered. Depending on the composition of the medium, development may lead either to the formation of embryoids and/or plantlets or a mass of parenchymatous callus. Four pathways based on the few initial divisions in the microspores have been identified as leading to in vitro androgenesis.

In pathway the microspores divide by an equal division and two identical daughter cells contribute to sporophyte development. Vegetative and generative cells are not distinctly formed in this pathway (e.g. Datura in noxia). In pathway 2 the division of uninucleate microspores is unequal, resulting in the formation of a vegetative and a generative cell.

The generative cell either does not divide at all or does so only to a limited extent. In pathway 4 the division of microspore is asymmetrical as in pathway 2. Both vegetative and generative cells divide further and contribute to development of the sporophyte (e.g. Datura metel, Atropa belladonna).

Irrespective of the above early pattern of microspore divisions, the embryogenic pollen grains ultimately become multicellular and burst open, gradually assuming the form of a globular embryo. This is followed by the normal stages of postglobular embryogeny until development of a plant.

Alternatively, the multicellular mass liberated from the bursting pollen grain proliferates to form callus which may later differentiate whole plants either on the same medium or on a modified medium. It is sometimes possible to obtain and rogenic haploids via embryo formation or through callusing within the same species (Oryza sativa) by manipulating constituents of a medium.