Atropa Belladonna (belladonna): The whole plant is harmful, but the fruits are the most dangerous, since they are deliciously sweet and tend to attract children. It takes 10 to 20 cherries to kill an adult, but just one leaf (in which the toxin is most concentrated) is enough to end a man's life. (The species can cause delirium and hallucinations. Other signs of belladonna poisoning include loss of voice, dry mouth, headache, breathing difficulties, and seizures).