The second method of seed dispersal is by clinging to the feet of native animals and humans. The small, black seeds become stuck in between the toes of animals and humans or in the tread of shoes. When the seed is eventually jolted out of its position, it falls to the ground and begins to germinate. Within two years it will have reproduced enough times to reach optimal density in a square metre, and gains another square metre or two every year from then on, with a possibly exponential growth rate.