Rafflesia or stinking corpse lily, is a genus of parasitic flowering plants in the family Rafflesiaceae. The species have enormous flowers, the buds rising from the ground or directly from the lower stems of their host plants; one species has the largest flower in the world. Plants of the World Online lists up to 41 species from this genus, all of them are found throughout Southeast Asia.
Western Europeans first learned about plants of this genus from French surgeon and naturalist Louis Deschamps when he was in Java between 1791 and 1794; but his notes and illustrations, seized by the British in 1803, were not available to western science until 1861. The first British person to see one was Joseph Arnold in 1818, in the Indonesia rainforest in Bengkulu, Sumatra, after a Malay servant working for him discovered a flower and pointed it out to him. The flower, and the genus, was later named after Stamford Raffles, the leader of the expedition and the founder of the British colony of Singapore.
The following is from Arnold's account of discovering the flower:
Here I rejoice to tell you I happened to meet with what I consider as the greatest prodigy of the vegetable world. I had ventured some way from the party, when one of the Malay servants came running to me ... To tell you the truth, had I been alone, and had there been no witnesses, I should, I think, have been fearful of mentioning the dimensions of this flower, so much does it exceed every flower I have seen or heard of.
Description
Replica of Rafflesia flower displayed in Philippine National Museum
The plant has no stems, leaves or roots. It is a holoparasite of vines in the genus Tetrastigma (a plant in the Vitaceae, the grape vine family), spreading its absorptive organ, the haustorium, inside the tissue of the vine. The only part of the plant that can be seen outside the host vine is the five-petalled flower. In some species, such as Rafflesia arnoldii, the flower may be over 100 centimetres (40 in) in diameter, and weigh up to 10 kilograms (22 lb). A Rafflesia that flowered in West Sumatra in 2019 was measured to be almost 4 feet (120 cm) in diameter, the largest flower ever recorded – 4 inches (10 cm) wider than the flower reported as the largest in 2017. Even one of the smallest species, R. baletei, has 12 cm (5 in) diameter flowers. A team of morphologists and geneticists headed by Prof. Charles Davis of Harvard has discovered an important difference between Rafflesia spp. and the very similar Sapria spp. In both genera the petals are now described as sepals (or more correctly as "petaloid tepals") instead of vaguely defined "perigon lobes". In Sapria, the "diaphragm" is a true corona while in Rafflesia the diaphragm is made up of adnate petals to form a dome, the true corona being greatly reduced.
The flowers look and smell like rotting flesh. The foul odour attracts insects such as carrion flies, which transport pollen from male to female flowers. Most species are dioecious, having separate male and female flowers, but a few (R. baletei and R. verrucosa) have hermaphroditic flowers. Little is known about seed dispersal. Tree shrews and other forest mammals eat the fruits. The extremely tiny seeds have extremely tiny elaiosomes, and are thus most likely dispersed by ants. The seeds are packed into berries, each of which contains hundreds of thousands of seeds.
Because Amorphophallus has the world's largest unbranched inflorescence, it is sometimes mistakenly credited as having the world's largest flower. Both Rafflesia and Amorphophallus are flowering plants, but they are unrelated to each other. Rafflesia arnoldii has the largest single flower of any flowering plant, at least in terms of weight. Amorphophallus titanum has the largest unbranched inflorescence, while the talipot palm (Corypha umbraculifera) forms the largest branched inflorescence, containing thousands of flowers; the talipot is monocarpic, meaning the individual plants die after flowering.
Rafflesia are also remarkable for showing a large horizontal transfer of genes from their host plants. This is well known among bacteria, but not higher organisms. It occurs in the mitochondria (originally derived from bacteria) found within the cells of Rafflesia; these appear to have exchanged genes with the mitochondria of the host tissue.
