page_title: Fertilisation of Orchids
section_title: Exotic orchids
hierarchical_section_title: Fertilisation of Orchids / Content / Exotic orchids
caption_attribution_description: English: Figure 29 from the 1877 edition of Charles Darwin's Fertilisation of Orchids. Scanned from a copy of the work at the University of Massachusetts Amherst.Illustration of Catasetum saccatum
context_page_description: 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.
context_section_description: The book moves on to the various foreign orchids Darwin had received from others. His experiments showed that the "astonishing length" of the 11​¹⁄₂ inch (290 mm) long nectary hanging from Angraecum sesquipedale flowers implied the need for an as yet unknown moth with a proboscis 10–11 inches (250–275 mm) long to pollinate these flowers in Madagascar. He viewed this as the outcome of a coevolutionary race, writing that "there has been a race in gaining length between the nectary of the Angræcum and the proboscis of certain moths". This wastefulness is familiar in modern terms as the idea of an evolutionary arms race, but was disturbing to biologists of the time who believed that adaptations were the outcome of benevolent divine purpose.
  Darwin described "the most remarkable of all Orchids", Catasetum, and showed how in these flowers, "as throughout nature, pre-existing structures and capacities [had been] utilised for new purposes". He explained the mechanism in which the pollen masses of the pollinium were connected by a bent stalk or pedicel to a sticky disc kept moist at the back of the flower. When an insect touched an "antenna" projecting from the back of the flower, this released the bent pedicel which sprang straight and fired the pollinium, sticky disc first, at the insect. In experiments, Darwin had imitated this action using a whalebone spring. He vividly illustrated how the flower ejected the pollinium with considerable force: "I touched the antennæ of C. callosum whilst holding the flower at about a yard's distance from the window, and the pollinium hit the pane of glass, and adhered to the smooth vertical surface by its adhesive disc."
caption: The mechanism by which Catasetum saccatum ejects its pollen is explained by a sectional illustration, shown here to the right of an earlier print showing the plant.
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