This article was pretty interesting, about the different types of tulips and how they split.
http://en.allexperts.com/q/Bul...
Also found this good article here on ATP:
http://garden.org/articles/vie...
I don't have much luck getting tulips to return here in Illinois. I get a good display the first spring, maybe a few isolated blooms here and there the second year, and then nothing.
I do have some of the species tulips, and they return reliably. They are tiny, though, and very low-growing, almost more like a crocus than what most people thing of as a tulip. They make great little pops of color along the borders of my beds, though!
(edited to add the second link!)