What is the name of those circular plants that roll in westerns?

Question

I don't even know if they're plants, but I assume. They're just kind of big dust balls that roll across the scene. It's often parodied.

Answer 1

It's the salsola, or tumbleweed.

http://en.wikipedia.org/wiki/Salsola

Answer 2

tumbleweed

"Salsola (also known as Tumbleweed, Saltwort or Russian thistle) is a genus of herbs, subshrubs, shrubs and small trees in the family Chenopodiaceae, native to Africa, Asia, and Europe; they typically grow on flat, often dry and/or somewhat saline soils, with some species in saltmarshes.[1] Recent genetic studies[2] have however shown that the genus as traditionally circumscribed is paraphyletic, and many species are likely to be transferred to other genera in the future."

Link to picture posted