Orchid flower (Bulbophyllum ambrosia). The complex structure of the flower includes a specialised petal (centre) called the lip. Either side are two of the sepals. Above are the reproductive parts of the flower (small brown spot) with the two normal petals on either side. At top is the third sepal. The shape and colour of the lip has evolved to attract pollinators to the flower. This orchid is found in China, and has sweet-smelling flowers. There are more than 30,000 species of orchids worldwide, many of which are grown as ornamental flowers.