Rafflesia arnoldi is the world's largest single flower. It was discovered in the Indonesian rain forest by Sir Stanford Raffles and Dr. Joseph Arnold in 1818. It has no leaves and hardly any stem, just a huge speckled 5-petaled flower over a meter across which smells like rotting meat. It is parasitic on a vine, spreading its roots inside the vine. The fruit is eaten by tree shrews.
The world's largest flower is Amorphophallus titanum; its individual flowers are arranged in a spadix.