If the watermelons that a farmer grows is seedless, then how will he have seeds to grow next year? how can there be seedless watermelon seeds if you cannot collect seeds from that variety of watermelon?

Talk about a good question !!!
I've never thought of that, Kennyso.
Hmmmmmm.... maybe the seedless type really means that there are a few seeds?
Not actually without any seeds?

Seedless watermelons are cross breeds better know as hybrids. Just like the offspring of a male donkey and a female horse, the mule is almost always sterile. Mule Reference

The seeds for seedless watermelons are bred in a similar fashion. The pollen from one particular variety is used to fertilize the stamen of a different variety. The resulting seed will produce fruit, but will be sterile.

A more scientific explanation is provided by wikipedia "Oddly enough, seedless watermelons are grown from seeds. These seeds are produced by crossing diploid and tetraploid lines of watermelon, with the resulting seeds producing sterile triploid plants. Fruit development is triggered by pollination and these plants must be grown alongside a diploid strain to provide pollen."

Hello!
I found this for ya:
http://www.walterreeves.com/food_gardening/article.phtml?cat=1&id=608

Hope it helps/works!

Thanks for your replies...I've always wondered but never got around to asking!

That's my plan for next year. I'm going to scatter some seedless melon plants in with Sugar Babys.