What is the main purpose of seeds in plants that have them?

 Fruit (pods or hulls etc) bearing seeds are a means of dispersal for plants because they are sessile and have no means to move once germination anchors them with roots. Seeds are the dormant propagules or the quiescent, dispersing agents of the next generation that travel away from the parent plant  in a disposal. This is why fruit/seeds are categorized by their dispersal by wind (hydrochoric) or by animals (zoochoric).

Explanation:

your answer is "the 1950's"