Very curious round plants, six to twenty inches high, usually purple all over, sometimes green and rarely white, giving a brilliant effect in the fall to the sandy wastes they inhabit. They are a mass of interlacing branches, with hardly any leaves, except at the base, and very small flowers. When their seeds are ripe, and they are dry and brittle, the wind easily uproots them and starts them careening across the plain, their seeds flying out by the way. They turn over and over and leap along, as if they were alive, bringing up at last against a wire fence, or some such obstacle, where perhaps a traveler sees them from the train and wonders at the extraordinary-looking, dry, round bunches. There are other Tumble-weeds, such as Tumbling Mustard, Sisymbrium allissimum, and Amardnthus dibits, not of this family.