Rafflesia arnoldii is a parasitic plant, without roots or leaves. The main body of the plant resides inside the host plant. The only visible parts are the flowers, which burst through the host plant’s bark as compact buds, and later the fruits. The flowers are up to 1 m in diameter, and their flesh is reddish-brown with white spots. Each flower is either male or female and consists of five lobes inserted on a cup-like structure. In the centre of the cup is a column with a disk. The anthers (male parts) or styles (female parts) are situated underneath the disk. The fruits are berries with minute seeds.
It is likely that only damaged roots or stems of a new host can be infected by seedlings of Rafflesia. The foetid smell of the flowers attracts carrion-flies (of the genera Lucilia and Sarcophaga). The pollen adheres to the backs of the flies, which do not seem to receive any reward from the plant.
Two varieties are known, the more common being R. arnoldii var. arnoldiifrom Sumatra and Borneo, the other one being R. arnoldii var. atjehensiswhich is only known from north Sumatra. The main difference between the two is that the central disk (or ramenta) is partly missing at the base of the central column in R. arnoldii var. atjehensis.
A race for discovery
The first botanist to find a specimen of a Rafflesia was the French explorer Louis Auguste Deschamps (1765-1842). He was a member of a French scientific expedition to Asia and the Pacific. During the expedition he spent three years on Java, where in 1797 he collected a specimen of what is now known as R. patma. During the return voyage in 1798, his ship was taken by the British, with whom France was at war, and all his papers and notes were confiscated. They did not see the light of day until 1954 when they were rediscovered in the Natural History Museum, London.
The British botanist Joseph Arnold (1782-1818) and the statesman Sir Thomas Stamford Bingley Raffles (1781-1826, founder of modern Singapore) collected a specimen of another Rafflesia species found by a Malay servant in Sumatra in 1818. Arnold contracted a fever and died soon after the discovery. Lady Raffles, who had also been present when the specimen was collected, finished the colour drawing that Arnold had started of the plant, and it was sent to Joseph Banks, along with the preserved material. Banks passed all the materials on to Robert Brown (1773-1858) of the British Museum and Kew's resident botanical artist Franz Bauer (1758-1840).
William Jack (1795-1822) who was Arnold’s successor in Sumatra, being aware that Deschamps, despite his loss of notes, could formally publish a name for the newly discovered genus at any moment, rushed to draft a description to ensure the credit went to a British botanist. This draft description was held in readiness, in case there was word that the French were about to publish, whilst waiting for the British Museum to produce a better-prepared version.
The generic name, Rafflesia (given i n honour of Sir Raffles), proposed by Brown (who had originally wanted to call it Arnoldii) after Joseph Arnold, was validated by S.F. Gray in his report of the June 1820 meeting of the Linnean Society of London, as published in the Annals of Philosophy in September that year. While the species Rafflesia arnoldii was officially described for the first time in 1821 by Brown, so that Arnold was commemorated after all.
Threats and conservation
Many sites where Rafflesia grows are now popular with tourists, who provide an income for local people and also an incentive to preserve the species. Unfortunately, as a result of this ecotourism and the resulting human disturbance, the number of flower buds produced per year has decreased significantly at many sites.
