Illustration of the structure of Orchis Pyramidalis from Charles Darwin's "On the various contrivances by which British and foreign orchids are fertilised by insects: and on the good effects of intercrossing" (1862). The complex mechanisms which orchids have evolved to achieve cross-pollination were investigated by Charles Darwin (1809-1882) and described in his 1862 book Fertilisation of Orchids. Orchids have developed highly specialized pollination systems, thus the chances of being pollinated are often scarce, so orchid flowers usually remain receptive for very long periods, and most orchids deliver pollen in a single mass. Each time pollination succeeds, thousands of ovules can be fertilized.