Acacias (pron. ah-cay-see-uhs) are a diverse group of trees related to beans (Family Leguminosae; Fabaceae in the US). Acacias are found throughout the tropics. Their range is restricted by cold winters as most species cannot survive frost. Acacias have characteristic "pinnate" leaves, comprised of tiny leaflets, and red or yellow flowers with many stamens that gives them a fluffy appearance. Many have tough thorns as they generally lack protective toxic compounds. A number of species are symbiotic with ants, which offer an additional level of protection. A well-known type acacias are the mimosas such as the Sensitive Plant (Mimosa pudica) which has leaves that close when touched.