Tumble Weed Clipart How Does Tumble Weed Tumble, And What Is It Anyway?

How does tumble weed tumble, and what is it anyway? - tumble weed clipart

There was a trip a few years ago and saw something falling giant grass taller than a car "case" by the way, and he was deeply impressed by its unusual structure fascinating. Before we only see them in National Geographic. Can someone tell me as much information as possible? Thanks