Fertilisation of Orchids is a book by 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.[1] Darwin's previous book, On the Origin of Species, had briefly mentionedevolutionary 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 a 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 inpollinating 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, and produced testable predictions. His proposal that the long nectary of Angraecum sesquipedale meant that there must be a moth with an equally long proboscis was controversial at the time, but was confirmed in 1903 when Xanthopan morgani praedicta was found in Madagascar. Darwin's speculations on the origin of species convinced him that cross-fertilisation played an important role in keeping specific forms consistent. He rejected the doctrine that the characteristics of a species were static, and was aware from animal husbandry that inbreeding could lead to changes, often deleterious. He thought that natural outbreeding through cross-fertilisation would keep wild species homogenous yet vigorous. Cross-fertilisation would confer an evolutionary advantage by spreading favourable changes throughout a reproductive community. His ideas were contrary to the common supposition that plants were usually self-fertilising, and so every summer Darwin investigated the contribution of insect pollination to the cross-pollination of flowers.[3][4] In the summer of 1841 Charles and Emma Darwin moved from the turmoil of London to the countryside, to Down House, a quiet former parsonage in the village of Downe. He wrote, "The flowers are here very beautiful".[5] Darwin followed the recommendation of his friend, the leading botanist Robert Brown, and read Das entdeckte Geheimnis der Natur im Bau und in der Befruchtung der Blumen (The Secret of Nature in the Form and Fertilisation of Flowers Discovered[6]).[3] The little known book, published in 1793 by Christian Konrad Sprengel but never translated into English, introduced the idea that flowers were created by God to fulfill a teleological purpose: insects would act as "living brushes" to cross-fertilise plants in a symbiotic relationship. This functional view was rejected and mostly forgotten, as it contradicted the common belief that flowers had been created for beauty, and were generally self-fertilising. For Darwin, the concept of evolution gave new meaning to Sprengel's research into the mechanisms for cross-fertilisation. He welcomed its support for his supposition that cross-fertilisation in flowering plants tended to allow their offspring to avoid possible disadvantages resulting from self-fertilisation,[7]and by 1845 he had verified many of Sprengel's observations.[8] A favourite walk took the Darwin family to a spot above the quiet Cudham valley, teeming with orchids includingCephalanthera, Neottia, fly orchids and musk orchids. They called this place "Orchis Bank", and the whole family became involved in Darwin's researches.[9] Darwin observed orchids every summer, but in twenty years, only on two occasions (when he noticed butterflies "sucking O. pyramidalis and Gymnadenia") did he see insects visiting flowers.[10] In 1854, Darwin began to work full-time on the origin of species.[11] He examined orchids and counted how often one or both pollinia (pollen masses) had been removed from their flowers, indicating that they had been visited by insects.[12] He experimented with insect pollination to investigate whether, by cross-fertilising field crops such as Fabaceae, they would yield more vigorous offspring, and published letters about his inconclusive results in The Gardeners' Chronicle in 1857 and 1858. He next applied Sprengel's methods toempirical research on orchids.[4][13] Despite delays caused by recurring illness, he made progress on writing his planned "Big Book" on evolution, but whenAlfred Russel Wallace's letter prompted joint publication of both of their theories of natural selection in 1858, Darwin quickly wrote On the Origin of Species as an abstract of his theory, published on 22 November 1859.[11] In this book, he gave credence to Sprengel's ideas on the advantages of "intercrossing",[14] and noted: "Many of our orchidaceous plants absolutely require the visits of moths to remove their pollen masses and thus to fertilise them".[15] He introduced his new concept, the process of coevolution, describing the co–adaptation of bumblebees and red clover, and speculating "how a flower and a bee might slowly become, either simultaneously or one after the other, modified and adapted in the most perfect manner to each other, by the continued preservation of individuals presenting mutual and slightly favourable deviations of structure." This was a theme he developed in his orchid book.[16][17] After On the Origin of Species was published, Darwin became involved in producing revised editions as well as working on Variation of Animals and Plants Under Domestication as the first part of his planned "Big Book".[18][19] By the spring of 1860 he had tired of the grind of writing, and needed something fresh and interesting to study. During a family visit to relatives at Hartfield, he was searching for orchids when he noticed a sundew. He collected it and tried to feed it insects, thus beginning a long-term study of insectivorous plants. He investigated otherbotanical questions raised by his ideas of natural selection, including the advantages of sexual dimorphism inprimulas, and the adaptive mechanisms that ensure cross-pollination in orchids.[20][21] As an enthusiastic practical scientist, such investigations gave him a strong sense of personal enjoyment. He relished pitting his wits against nature, and following lucky hunches. His theory was a way of looking at the world, enabling him to find creative solutions to problems that traditional approaches could not solve. He later wrote, "I am like a gambler, & love a wild experiment."[22][23] Around the end of April 1860, Darwin discussed insect pollination with his friend Joseph Dalton Hooker,[24] and mentioned the bee orchid.[25] Darwin corresponded with Hooker's assistant Daniel Oliver, the senior curator atKew Gardens, who became a follower of Darwin's ideas.[22] At the start of June, Darwin wrote to The Gardeners' Chronicle asking for readers' observations on how bee or fly orchids were fertilised. His letter described the mechanisms for insect fertilisation he had discovered in common British orchids, and reported his experimental observations that pollen masses were removed from Orchis morio and Orchis masculaplants in the open, but left in their pouches in adjacent plants under a glass bell jar.[26] He wrote to American botanist Asa Gray that he had been "so struck with admiration at the contrivances, that I have sent notice to Gardeners Chronicle",[27] and made similar enquiries of other experts.[28] Darwin became engrossed in meticulous microscopic examination, tracing the complicated mechanisms of flowers that attracted insects by their nectar so that the insects transported pollen to cross-pollinate other plants, and on 19 July he told Hooker, "I am intensely interested on subject, just as at a game of chess."[21][29] In September, he "dissected with the greatest interest" and wrote, "The contrivances for insect fertilisation in Orchids are multiform & truly wonderful & beautiful."[30] By October, he had "a large mass of notes with many new facts", but set them aside "convinced that I ought to work on Variation & not amuse myself with interludes".[31] During 1861, botany became a preoccupation for Darwin, and his projects became serious scientific pursuits. He continued his study of orchids throughout the summer, writing to anyone who might be able to supply specimens he had not yet examined.[32] Field naturalists, botanists, and country gentry sent specimens from across the British Isles. Darwin also tramped around the countryside with tin cans and biscuit boxes, collecting specimens which his gardeners potted up for him. His family joined in, and neighbours contributed to the research. As he had only a cold greenhouse, a friend on the other side of the village who had a hot-house allowed him to use that, and offered the services of his gardener to look after the delicate specimens. Darwin's aim was to show how the complex structures and life cycles of the plants could be explained by natural selection rather than by the handiwork of God; he saw the huge variety of flowers as a collection of ad hoc evolutionary adaptations.[33] In June he described his examination of bee orchids as a passion,[34] and his findings on insect fertilisation of orchids as "beautiful facts".[35] There were several replies to Darwin's enquiry in The Gardeners' Chronicle seeking evidence to support his idea that pollen masses attached themselves to a convenient place on an insect's back or head, usually its proboscis, to transport the pollen to another flower. One envelope appeared to be empty when it arrived at Down House, but when he looked further before discarding it he found several insect mouthparts with pollen masses attached.[36] To help their daughter Henrietta convalesce from illness, the Darwins arranged to spend two months in Torquay. Darwin wrote: He sought advice on obtaining the exotic South American Catasetum, to see it eject pollen masses, as "I am got intensely interested on subject & think I understand pretty well all the British species."[37] They went to Torquay on 1 July,[38] and Darwin began writing his Orchid paper.[39] By 10 August, he feared his paper would run "to 100 M.S. folio pages!!! The beauty of the adaptations of parts seems to me unparalleled ... I marvel often as I think over the diversity & perfection of the contrivances."[40] The family returned to Downe on 27 August,[38] and Darwin again wrote to the Gardeners' Chronicle appealing for assistance as he was "very anxious to examine a few exotic forms."[41] His requests to the wealthy enthusiasts who had taken up the fashionable pursuit of growing rare orchids brought large numbers of specimens. These would be a test of his theory: previously aspects such as coloration of plants and animals had often been regarded as having no adaptive function. For example, Thomas Henry Huxley was strongly influenced by German idealismand in 1856 had asked if it was "to be supposed for a moment that the beauty of colour and outline ... are any goodto the animals? ... Who has ever dreamed of finding an utilitarian purpose in the forms and colours of flowers ... ?" Darwin had, and in the orchids he tackled the most difficult case. His ideas would transform the way naturalists thought about coloration.[42][43] The completed Orchis paper came to 140 folio pages, and Darwin decided against presenting it at the Linnean Society of London, thinking of publishing a pamphlet instead. He offered the draft to John Murray who agreed to publish it as a book.[44] Although Darwin feared a lack of public interest, he hoped it would serve to "illustrate how Natural History may be worked under the belief of the modification of Species."[45] In discussions with Asa Gray about natural theology, he wrote that "it really seems to me incredibly monstrous to look at an orchid as created as we now see it. Every part reveals modification on modification."[46]Charles Darwin grew up with an interest in natural history, and as a student at the University of Cambridge he became a pupil and close friend of botanyprofessor John Stevens Henslow. The year he graduated, Darwin was given a position as a gentleman naturalist and geologist on the second voyage of HMSBeagle, a trip that lasted five years. By the time he returned in October 1836, he had doubts about the doctrine that species were fixed and unchanging. Within months, experts informed him that specimens he had collected were separate species, not just varieties, and the patterns he saw inspired the inception of his theory of natural selection in 1838. Darwin began editing and publishing the expert reports, collected in the Zoology of the Voyage of H.M.S. Beagle, at the same time as writing a series of books on geology, the first of which was The Structure and Distribution of Coral Reefs. His "species work" was his "prime hobby", a background to this writing, but it evolved into an extensive research programme during the twenty years before he published his theory.[2][edit]Background
[edit]Insect fertilisation of plants
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[edit]Botany as recreation
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[edit]Research and draft
Saturday, October 9, 2010
Orchid fertilization & other orchid information
I have, owing to many interruptions, not been going on much with my regular work (though I have done the very heavy jobs of variation of Pigeons, Fowls, Ducks, Rabbits Dogs &c) but have been amusing myself with miscellaneous work.—I have been very lucky & have now examined almost every British Orchid fresh, & when at sea-side shall draw up rather long paper on the means of their fertilisation for Linn. Socy & I cannot fancy anything more perfect than the many curious contrivances.[37]
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