How do plants with seedless fruit reproduce?

We see two bananas in peels and one cut in half, with its seeds exposed.

Sinking your teeth into a juicy, ripe watermelon is one of summer's greatest pleasures, particularly when you don't have to spit out any seeds. Indeed, humans have adapted many fruits to be seedless in pursuit of a more pleasant eating experience. 

But without seeds, how do such plants reproduce?