When RNA synthesis is blocked with actinomycin D (AmD) at the start of germination of Tradescantia paludosa L. pollen, the division of the degenerative cell is completely prevented. AmD added 3 h or later after start of germination does not affect the division. The RNA species required for division are hence synthesized during the first 2–3 h of pollen tube growth. When protein synthesis is blocked with cycloheximide (CX) at the start of pollen germination, progress of the generative cell towards division is completely blocked. If CX is added 1 or 2 h after start of germination, a large number of cells are blocked in metaphase. If applied 4 h after germination, CX does not prevent the formation of the two sperm cells. The proteins synthesized during the first 2 h of germination and growth thus seem to be required for the early stages of mitosis, and during the next 2 h the proteins required for the completion of the division are synthesized. A comparison of the time intervals when AmD and CX are effective in blocking generative cell division indicates that the RNA species required for division are synthesized during the first 2–3 h of growth and the translation of at least some of these RNA's into proteins is required for the completion of the division.