Anthers of Nicotiana tabacum cv. White Burley containing microspores in mitosis were cultured for 12-14 d at 23° C in order to induce mitosis of the vegetative cell (embryogenic grains). After this period the total DNA content of such grains estimated by gallocyanin-chrome alum photometry was double that of the microspores in mitosis, whereas the total RNA content was reduced by about one-third. Total protein estimated by naphthol yellow S photometry was approximately the same as at inoculation. In contrast, total RNA and total protein contents of non-embryogenic grains in the same anthers were at least four times greater than at inoculation. It is suggested that degradation of cytoplasmic information concerned in gametophytic differentiation takes place prior to mitosis of the vegetative cell.