Charles Darwin

by Janet Browne

  In practical terms, Darwin’s experiment in this area was perhaps neither more nor less than any other natural historian or amateur botanist might have pursued for amusement during the early summer months. Yet he brought to it an over-riding preoccupation with the consequences of the results. This feature of his practical work remained constant throughout a long life. Every experiment he was to devise in future years was performed with its ultimate relevance for evolution by natural selection in mind. He rarely tried things out merely to see what might happen—or at least, even his most improbable inquiries were executed with some hypothesis or “wild speculation” to explore.4 “He often said that no one could be a good observer unless he was an active theoriser,” remarked his son Francis much later on.

  It was as if he were charged with theorising power ready to flow into any channel on the slightest disturbance, so that no fact, however small, could avoid releasing a stream of theory, and thus the fact became magnified into importance. In this way it naturally happened that many untenable theories occurred to him; but fortunately his richness of imagination was equalled by his power of judging and condemning the thoughts that occurred to him. He was just to his theories, and did not condemn them unheard; and so it happened that he was willing to test what would seem to most people not at all worth testing.… The love of experiment was very strong in him, and I can remember the way he would say, “I shan’t be easy till I have tried it,” as if an outside force were driving him.5

  That “outside force” was the notion of natural selection. Furthermore, Darwin must have had a firm belief—or a naïve belief—in the possibility of getting answers from his work. As often as not, experimental science goes nowhere. It either runs into a dead end or provides results that cannot be used in the way that was intended. Experiments frequently fail and a new route into the problem has to be devised. Small-scale investigations like Darwin’s carried the additional hazard of being so small as to be insignificant to the larger scheme of things, barely a drop in the intellectual ocean. Nonetheless, Darwin seems to have convinced himself that the hours of work that he dedicated to counting seeds or measuring seedlings would be pertinent. “Another quality which was shown in his experimental work, was his power of sticking to a subject; he used almost to apologise for his patience, saying that he could not bear to be beaten, as if this were a sign of weakness on his part,” continued Francis. “Perseverance seems hardly to express his almost fierce desire to force the truth to reveal itself.”

  This faith in the power of practical work showed Darwin at his most pragmatic. He evidently believed that the best kind of biological science, the science that was taking shape as a discipline during the middle years of the nineteenth century, ought to be based on a culture of tangible experience. He felt confident that the solutions he wanted resided somewhere in his raw materials. His self-appointed task was to find them.

  III

  After this encouraging start, Darwin eased into a happy summer of orchids. For it was the existence of even more complicated reproductive adaptations in orchids that so fascinated him. Orchid flowers, which normally contain both male and female reproductive organs, do not usually fertilise themselves, he insisted, despite the proximity of the sexual parts. Instead, he thought the internal anatomy was arranged to ensure that the male pollen must be carried by an insect to another plant or flower, and that the female organs always received pollen from another source. In British and European orchids the process almost always involved bees, first described by Conrad Sprengel in 1793. Darwin thought Sprengel’s book was “wonderful,” and liked to praise the neglected merits of its author.6 Long ago Darwin too had noticed the internal structure of wild orchids and surmised that bees and moths carried pollen from one flower to the next.

  But this was only the half of it. In his garden or thereabouts he could find several native kinds. The unobtrusive green-winged orchid (Orchis morio) came up with the cowslips in the field, and the common orchid, Orchis mascula, usually known as Shakespeare’s long purples, arrived later, in the wooded area by the Sandwalk, the copse at the end of the Down House estate. There were other sorts on banks and ditches within a short walk; “no British county excels Kent in the number of its orchids,” he said appreciatively. The lower lip of the flowers, on which the insects landed, was either lobed or frilled, ornamented with coloured spots and patches, and sported any number of hairs, ridges, keels, wings, or spurs. The thought that these were lures for insects was unavoidable. Further inside, the male pollen masses were attached to thin, flexible stalks, like a pair of fragile, movable antennae, and, just below, what appeared to be the top of the female organs expanded out into a flat sticky plate or rostellum. The size, shape, and positioning of these male and female parts were different in every species. Darwin wondered about their origins, and how the flowers could possibly function. His intention was to show that even the most complex structures and life cycles, even those that depended on completely different organisms such as insects for their fulfillment, could be explained by natural selection. Where most people tended to regard plants like orchids as the handiwork of God, Darwin saw the flowers as a marvellous collection of ad hoc evolutionary adaptations.

  Armed with an array of tin cans and biscuit boxes to serve as containers, Darwin tramped the countryside in search of orchids, getting Brooks and Lettington to pot up the specimens he brought back. These employees had to stretch their traditional vegetable-garden repertoire to cope with a variety of demanding species that eventually included Epipactis latifolia, a woodland orchid which changes shape according to soil conditions, and Goodyera repens, a native of Scotland, which requires special bedding-out in peat all on its own. Darwin discovered it was best for his experiments if he dug up the whole plant, roots and all. He needed a ready supply of flowering spikes and access for observations in situ. The difficulties of germination (he did not know that many required the presence of a special fungus) and the long wait for the flowers to appear on mature plants made them an additional challenge.

  Inevitably, too, he began corresponding with field naturalists, horticulturists, botanists, and country gentlefolk who might be able to help. These contacts—especially Alexander More, who lived on the Isle of Wight, a site of special botanical interest—sent him native orchids from various parts of the British Isles. Alexander More often put fresh plants on the overnight train to Farnborough, and Parslow, the butler, would ride down to the station to collect whichever carefully sealed package had arrived that day.

  Darwin also began manoeuvring among a new group of correspondents, this time botanical women. As a subject, botany then enjoyed enormous popularity with nonprofessionals and was often associated in the public mind with respectable middle-class activities such as gardening and flower-painting. It was also particularly popular with women.7 On John Lindley’s advice, Darwin approached Lady Dorothy Nevill, the political hostess, to ask if she might be able to send him a few hothouse orchids from her collection. Lady Dorothy was an avid reader, writer, and gardener who became very much interested in the Origin of Species. Her hothouses—as Darwin hoped—contained unusual plants sent to her by friends from several parts of the world. In his first letter to her, he was beguilingly candid about his exotic desires, saying he would very much like “Limodoridae, Vanillidae &c, especially Mormodes & Cycnoches, Bonatea, Masdevillia, and any Bolbopyllum with its lower lip or labellum irritable.”

  Lady Dorothy collected famous botanists rather as she collected plants. She evidently considered Darwin a good catch. “I am so pleased to help in any way the labours of such a man—it is quite an excitement for me in my quiet life, my intercourse with him. He promises to pay me a visit when in London. I am sure he will find I am the missing link between man and apes,” she told Lady Airlie.8 In return, Darwin was willing to be caught if it meant that he got his specimens. Over the years Lady Dorothy sent him several rare plants. She also asked for his photograph to hang, as she said, in her private sitting room opposite Sir
William Hooker, a trophy gallery to which Darwin assigned himself with a sigh. His other lady acquaintances were usually less demanding.

  Through Hooker, Darwin also acquired introductions to a series of highly competent garden directors in the colonies, and to the botanical brothers Roland and Henry Trimen, working in South Africa and Ceylon respectively, each of them a mine of useful information.

  Family outings contributed to the cause. During one long and energetic morning while staying at Elizabeth Wedgwood’s house, Darwin transplanted Malaxis paludosa, the marsh orchid, from one boggy patch to another to see if insects were prepared to visit an intruder. Covered in mud, he returned to say that the insects did. At another time, his son George remembered being sent out to Cudham on a balmy summer night to catch and count the moths visiting plants on Orchis Bank, followed by an evening spent sitting at his father’s table surrounded by printed catalogues identifying the species. Once or twice Parslow put on leather gaiters to gather flower spikes from a ditch. When his master’s supply ran low, he took the London train to collect choice government specimens from Hooker.

  Darwin’s neighbours were similarly obliging—his was a passion that could be understood and indulged. George Turnbull, of the Rookery on the other side of the village, let Darwin use his heated greenhouse for the more delicate specimens that came into his hands, and tolerantly watched as his own gardener, John Horwood, was swept into Darwin’s voracious information system.9 Horwood was more knowledgeable than Darwin’s own gardeners and had experience with hothouse cultivation techniques. On one occasion, he was the only person able to identify plants that arrived from Kew without their labels. Probably gratified at being able to display his professional expertise, Horwood went on to fertilise Vinca rosea for Darwin, a demonstration of technical virtuosity that he undertook only when several contributors to the Gardeners’ Chronicle recorded constant failure.

  Moreover, Darwin was fortunate in being able to tap the horticultural vigour of the times. He benefitted greatly from the surge in botanical expertise that characterised the Victorian temper of life, the new clubs, societies, training schemes, glasshouses, heating systems, illustrated magazines, and libraries. He obtained easy access to an abundance of specialist nurserymen and seedsmen, plant breeders, gardening authors, and skilled practical men, all of whom contributed in one way or another to the great fervour for plants that marked the middle years of the nineteenth century. Rapid developments in glasshouse technology were benefitting amateurs and professionals alike, at the same time as new trade routes and overseas connections made the importation of fancy species more feasible, and the restless urges of the middle classes were spilling into natural history fashions and crazes as never before. Botany, with all its ramifications into colonial enterprise, the plantation system, horticulture, herbarium research, agriculture, recreation, and fashion, was the “big science” of its day as well as a rising popular phenomenon. Plant breeding became an absorbing hobby for some, the backbone of a prime business concern for others. Horticulture diversified into profitable commercial propositions as new forms of stoves, plate glass, iron girders, mechanical ventilation systems, pipework, and the park-keeper’s urge for gaily coloured bedding-out schemes in leisure gardens all came into being in the middle years of the century. Although Britons have historically always considered themselves a nation of gardeners, there was something unique about this particular combination of plants, business acumen, public attention, and technology that generated unprecedented attention.

  There could hardly have been a better time to take up the study of orchids either. The Royal Botanic Garden at Kew naturally involved itself with the tropical species, making full use of Britain’s ascendency overseas to collect a wide variety of species. These were essentially plants for research and colonial display. At the same time, the Horticultural Society in London (soon to add “Royal” to its name) encouraged its members to grow show specimens, building an orchid house in the society’s public gardens at Chiswick and stimulating the growth of commercial firms such as James Veitch & Sons, which built up a successful business in breeding new blooms. In 1859 the Horticultural Society awarded its first Certificate of Outstanding Merit at a show to a cattleya bred by James and John Veitch. This previously rather specialised taste for orchids developed into a vogue during the 1860s and 1870s, rather as tulipomania had gripped Europeans in the seventeenth century and pinks and auriculas excited pre-war gardeners in the early twentieth.10 Reputations soared with the development of a single exceptional bloom. Incomes improved; botanical skill, determination, and personal endeavour were rewarded.

  Few enthusiasts succeeded in keeping their orchids alive for very long. Early misunderstandings about potting techniques and temperatures defeated nearly everyone, and fresh specimens were constantly imported to replace the old. Looking around the stalls at one horticultural show, Hooker sadly remarked that England was the “grave of tropical orchids.” He referred to the depredations around Rio de Janeiro, an area where Darwin had collected only thirty years before, which was subsequently stripped of all its native orchids, never to reappear.

  Still, Darwin had a ready-made resource at his fingertips.11

  IV

  He had noticed one of the more unusual adaptations before. Standing in his study one day he was tinkering with an orchid flower when the pollen masses suddenly shot out and hit the window: “about a yard’s distance,” he said in surprise. He tried to detonate other orchids by inserting thin paintbrushes and pencils into the mouth of the flowers. Few of them possessed similar high-velocity devices. But if he looked carefully, the pollen masses all displayed an ability to move on their stalks—a feature which had previously been mentioned in print by William Herbert, Henslow’s botanical friend, and some other authors. Even so, Darwin seems to have been one of the first naturalists to ask what this movement might mean in terms of insect visitors. He decided that the pollen masses must bend or shoot themselves into the right position to stick onto an insect’s back or head (usually the proboscis) for transfer to another flower. He had inquired about this possibility in the letter column of the Gardeners’ Chronicle in 1860, and received a number of replies. One answer arrived at Down House only as an empty envelope. Just before he threw it away, Darwin investigated further. Tucked away at the bottom he found a number of insect mouthparts laden with tiny parcels of pollen.

  He also noticed a secondary reflex movement of the pollen masses (pollinia) after they were detached from the flower. He timed these movements with his pocket watch, finding they usually took around thirty seconds, just long enough for the bee to which they would usually be attached to push into another flower. His fancy ran away with him.

  A poet might imagine that whilst the pollinia were borne through the air from flower to flower, adhering to an insect’s body, they voluntarily and eagerly placed themselves in that exact position in which alone they could hope to gain their wish and perpetuate their race.12

  More to the point, adaptive evolution, proceeding blindly and without any foresight or plan, could explain an exquisite feature of natural life that would otherwise be regarded as convincing evidence for God-given design.

  His work on orchids thereafter deliberately addressed the issue of design. To account for the apparent design of the living world, after all, had been the central plank of his argument in the Origin of Species and these plants gave him an opportunity to demonstrate the actual adaptive ingenuity of nature, his answer to William Paley’s natural theology, the secular alternative to divine craftsmanship. When he came to publish this work he told Asa Gray decisively that his orchid studies represented “a flank movement on the enemy.”13

  The issue rode particularly high in his mind at this time because of Gray. In a series of letters to Darwin stretching from 1860 to 1862, and emerging out of his reading of the Origin of Species, Gray interrogated Darwin about the origin of design in nature. Gray believed that the apparently perfect adaptions that the natural world exhibited�
��as in the mutual co-adaptations between insect and plant—reflected the thought and intent of a Creator, however such a deity might be understood. But he also recognised the efficacy of Darwin’s notion of natural selection. In letters and reviews he volunteered a compromise solution in which favourable variations were perhaps produced by the hand of God. Natural selection would then pick or select these in the competition for life. Gray, in effect, wanted to have it both ways. God would carry on supervising nature, for it was the Almighty who introduced favourable variants. And natural selection would act just as Darwin had proposed, as an objective, mechanical, winnowing force which tailored organisms to their surroundings. In making this suggestion, Gray was to differ markedly from other creative evolutionists or those who advocated providential evolution. He gave Darwin his due and did not make God the selecting agent.

  Darwin understood the dilemma. Gray was not advocating traditional forms of divine creation. The botanist William Harvey, Hooker’s friend, had written to Darwin in an altogether stricter manner, saying that “the Divine Creator” could call up “without seed, from the dust of the ground a new organism, by the power of his omnipotent word.” Gray was suggesting something much subtler, a form of divinely directed evolution. The threat was not lost on Darwin. If established, it would have destroyed the meaning of natural selection and any hope of a positivistic biology.