The activation of the pollen grain of Tradescantia paludosa during germination is accompanied immediately by the initiation of protein synthesis. About 38 % of the ribosomes in ungerminated pollen grains are in polysomes. During germination there is a very rapid formation of additional polysomes beginning within as short a period as 2 min. A fraction of the ribosomes in the ungerminated pollen grain appears to be prepackaged with messenger RNA (mRNA), defined by the sensitivity of polysomes to dissociation by mild ribonuclease treatment. © 1969.