Cactaceae, the cactaceae, are collectively known as cacti, cacti, or cacti. This family is native to America. However, there is one exception, Rhipsalis baccifera, which is widespread in tropical Africa, Madagascar, and Ceylon. Colonization of the Old World by this species is believed to be relatively recent (a few hundred years), probably carried in the digestive tract of migratory birds in the form of seeds, either directly from America or from populations arising in Africa as a result of slave transport. Many succulent plants, both in the Old and New Worlds, bear a striking resemblance to cacti and are often so called in ordinary language. However, this is due to parallel or convergent evolution (similar selective pressures result in similar morphologies), since none of them is closely related to cacti. The clearest identifying feature of the cactus family is the areola, a specialized structure from which thorns, new stems and, in many cases, flowers, arise.