Castor oil plant (Ricinus communis). Each spiny seedpod of this plant contains on average three seeds, from which castor oil is extracted for medicinal use. Castor oil is taken for its laxative effects, however another component of the oil is ricin, one of the most powerful poisons known. Ricin has been used in the treatment of cancer, as it can be targeted to destroy cancer cells whilst leaving normal cells untouched. The castor oil plant is a very fast growing tropical shrub or small tree, which can reach up to 10 metres in height. Photographed in Barbados.