Fertilisation of Orchids

Fertilisation of Orchids is a book by English naturalist Charles Darwin published on 15 May 1862 under the full explanatory title On the various contrivances by which British and foreign orchids are fertilised by insects, and on the good effects of intercrossing. Darwin's previous book, On the Origin of Species, had briefly mentioned evolutionary interactions between insects and the plants they fertilised, and this new idea was explored in detail. Field studies and practical scientific investigations that were initially a recreation for Darwin—a relief from the drudgery of writing—developed into enjoyable and challenging experiments. Aided in his work by his family, friends, and a wide circle of correspondents across Britain and worldwide, Darwin tapped into the contemporary vogue for growing exotic orchids.

The book was his first detailed demonstration of the power of natural selection, and explained how complex ecological relationships resulted in the coevolution of orchids and insects. The view has been expressed that the book led directly or indirectly to all modern work on coevolution and the evolution of extreme specialisation. It influenced botanists, and revived interest in the neglected idea that insects played a part in pollinating flowers. It opened up the new study areas of pollination research and reproductive ecology, directly related to Darwin's ideas on evolution, and supported his view that natural selection led to a variety of forms through the important benefits achieved by cross-fertilisation. Although the general public showed less interest and sales of the book were low, it established Darwin as a leading botanist. Orchids was the first in a series of books on his innovative investigations into plants.

The book describes how the relationship between insects and plants resulted in the beautiful and complex forms which natural theology attributed to a grand designer. By showing how practical adaptations develop from cumulative minor variations of parts of the flowers to suit new purposes, Darwin countered the prevailing view that beautiful organisms were the handiwork of a Creator. Darwin's painstaking observations, experiments, and detailed dissection of the flowers explained previously unknown features such as the puzzle of Catasetum, which had been thought to have three completely different species of flowers on the same plant. In addition, they produced testable predictions including his then-controversial proposal that the long nectary of Angraecum sesquipedale meant that there must be a moth with an equally long proboscis. This was confirmed in 1903 when Xanthopan morgani praedicta was found in Madagascar.