Charles Darwin was quite an artist. No, not that kind—he appreciated the visual arts but was hopeless with a sketchpad, let alone a canvas—his aptitude for drawing was perhaps second-to-last in any ranking of his abilities (his handwriting, notoriously illegible, no doubt coming in at the bottom). But Darwin was surely an artist of science—an artful asker of questions and crafter of studies both observational and experimental. There is, after all, an art to science—beauty in theory, elegance in experimental design, a satisfying harmony in the consilient resonance of supporting evidence. Of course, Darwin would not have described his work as “beautiful” or “elegant”—in fact, just the opposite. “I love fools’ experiments,” he quipped to one visitor. “I am always making them.”1 He liked to poke fun at himself, but there is no question that the self-described “experimentiser” was a master of composition and had a deft touch when it came to those “fools’ experiments”—myriad curious research projects unfolding everywhere from his gardens and greenhouses to the meadows and woodlands around Down House, his home of forty years just south of London. That home was a veritable research station, with Darwin as chief scientist and his wife, children, extended family, servants, and friends his ever-obliging research assistants. Many a correspondent helped too, some recruited through Darwin’s many “crowd sourcing” letters to magazines and newspapers.
Darwin is best known for his masterwork On the Origin of Species, published in 1859, a book that he described as “one long argument.” What he meant by that is most evident in the topics treated in the second half of the book, with chapters dedicated to a diversity of subjects (behavior, fossils, geographical distribution, comparative anatomy, and more), lines of evidence that, he argued, were collectively united and explained by his theory of evolution by natural selection. The fame of Origin tends to overshadow the fact that Darwin followed it with some dozen more books, beginning with his curious volume on orchid pollination mechanisms in 1862. How odd, some thought, to follow so sweeping a book as Origin with one so narrowly focused. But there was method to the madness: the orchid book signaled the direction his work would take for the next twenty years—a corpus of work that was Origin writ large, myriad subjects with an eye to extending and reinforcing the explanatory power of his theory. It was, collectively, one longer argument. The orchid book also signaled a new favorite research subject: plants. Half of his post-Origin books treated botanical subjects—climbing plants following orchids, then carnivorous plants, forms of flowers, pollination, and more. Darwin didn’t consider himself a competent botanist, but his friends knew better—Asa Gray, at Harvard, applauded and encouraged his botanical investigations, writing, “it will be fruitful in your hands.”2 The metaphor was more appropriate than Gray may have anticipated; Darwin’s botanical investigations grew, blossomed, and bore rich fruit in the form of remarkable new discoveries, launching whole new disciplines that have themselves grown and continue to bear fruit today. For a self-described amateur when it came to botany, Darwin sure had a green thumb when it came to growing both a garden and ideas.
Photo of Charles Darwin at age seventy-two on the veranda at Down House, with Parthenocissus twining up the post. Photo taken in 1881 by Messers. Elliot and Fry, published in The Life and Letters of Charles Darwin (1887).
Some might say he came by these talents honestly. Charles Darwin was born on 12 February 1809, the second son of physician Robert Darwin and Susannah Wedgwood. The families on both sides were accomplished: Robert was the son of the famed physician and poet Erasmus Darwin, friend to a “who’s who” of Enlightenment Britain’s intellectual circles, whose best-selling poetry extolled scientific subjects, including the famous The Loves of the Plants—an at-times-titillating exposition of Linnaeus’s sexual system of botany. Susannah was the daughter of Josiah Wedgwood, founder of the celebrated pottery works and prominent member of those intellectual circles frequented by Erasmus—they were friends with and founding members of the Lunar Society, that remarkable circle that included among others James Watt (of light bulb wattage), industrialist Matthew Boulton, pioneering chemist Joseph Priestley (discoverer of the element oxygen), and corresponding member Benjamin Franklin, the celebrated American statesman and inventor. An appreciation of flowers and gardens was very much in the tradition of both families. Charles Darwin’s childhood home, The Mount, in the bustling market town of Shrewsbury, featured a bounteous hillside garden, and the gardens and pleasure grounds of nearby Maer, the Wedgwood estate, were originally laid out by Capability Brown. Darwin’s cousin and future wife Emma Wedgwood, grew up there, reveling in those gardens; he used to say that Emma only cared for flowers that were grown at Maer.3
But it’s fair to say that, for Charles Darwin growing up, flowers and gardens were more backdrop, a theater for childhood romps, than interest per se, and as an affable teen he was mostly into riding his horses and hunting with his dogs (though there was the smelly chemistry lab he set up in the stables with his older brother ‘Ras). As for future profession, there was no question: in the family tradition he would become a doctor; he was duly packed off to Edinburgh at age sixteen to join ‘Ras in medical school. That didn’t work out too well. After witnessing a couple of horrific operations, one on a child, he quickly discovered that he couldn’t stomach the blood and screaming. He left Edinburgh after two years, heading to Cambridge where he was expected to prepare for a career in the church (country parson was a perfectly respectable profession for someone of his social class). Edinburgh had not been a total bust, however. In his time there, he studied zoology with Robert Edmond Grant, who introduced him to the fascinating world of marine invertebrates (on which Darwin conducted his first research project) as well as the somewhat disreputable world of unorthodox theorizing. Grant had studied in Paris and was a devotee of French savant Jean-Baptiste de Lamarck, who had developed an elaborate theory of species change, or “transmutation.” Such unorthodox ideas, deemed contrary to scripture, had only been tolerated in Britain since the bitter aftermath of the terror in France, when transmutation became synonymous with revolution, even sedition. The young Charles Darwin was no wild-eyed revolutionary—he had no interest in such scandalous ideas and shrugged off his professor’s transmutationist musings. Yet a seed was planted.
Moving on to Cambridge, he commenced training for the church. But that was not to be either, thanks largely to beetles and botany. On the beetling front, Darwin was caught up in collecting, then all the rage among the undergraduates (puzzling as that may be to modern readers!). A taste for natural history was not contrary to the country vicar’s life—just the opposite, as Britain had (and has) a great tradition of talented and accomplished vicar-naturalists, and Darwin came under the influence of one such, the kindly Reverend John Stevens Henslow, professor of botany. A clergyman like all Cambridge faculty, Henslow led legendary botanizing rambles after church each Sunday. Darwin was often in attendance and more and more taken with his professor and the subject, becoming known as “the man who walks with Henslow.” He was excited by geology too, an up-and-coming science offering astounding new insights into earth’s antiquity—Darwin found his professor, Reverend Adam Sedgwick, a “capital hand” at drawing “large cheques on the bank of time.”4 As his interest in natural history grew steadily stronger, Darwin’s fate may have been sealed with his reading of the great Alexander von Humboldt, the German polymath whose electrifying Personal Narrative chronicled his explorations in Mexico and northern South America and inspired a generation of naturalists to travel, observe, and study nature holistically. Darwin started scheming, hoping to convince a band of friends to travel with him to the Canary Islands to follow in Humboldt’s footsteps. That trip ended up fizzling, but Darwin’s disappointment evaporated when another, even more exciting prospect was presented thanks to Henslow: a voyage around the world on the Royal Navy surveying ship HMS Beagle, as naturalist and gentleman-companion to the captain, Robert Fitzroy.
The only fly in the ointment was his father. Robert Darwin was less than pleased with this “wild scheme.” Wanting his son to take holy orders and settle down already, he put his foot down—this was a waste of time, and possibly damaging to Charles’s future prospects in the church. Evidently however, he gave a caveat: if any respectable person with good sense could give him reasons why his son should go on such a voyage, he might reconsider. A despondent Darwin saddled up his horse and headed to Maer, where his uncle, Josiah Wedgwood II, lent a sympathetic ear—and proved to be just the respectable and sensible person needed, helping Darwin make a case to his father.5 It worked, and over the next five years, Charles Darwin had the ride of his life, making extensive geological observations (thanks to a crash-course in field geology with Sedgwick) and collecting fossils, zoological specimens, and lots and lots of plants.
The animals Darwin encountered get most of the attention—fascinating finches and charismatic mega-fauna like the giant tortoises of Galápagos and even larger extinct beasts of the South American mainland, including great armadillo-like Glyptodon and the elephant-sized ungulate Toxodon. But Darwin himself was about as taken with the plants. Musing over the birds of Galápagos, Darwin noted in his journal that “I certainly recognise S. America” in their affinities but also wondered “would a botanist?”6 And later, again musing on the significance of Galápagos species, he declared that “the botany of this group is fully as interesting as the zoology.”7 On his return, Darwin hoped that his old mentor Henslow would analyze his South American plants. Up to his neck in work, however, Henslow didn’t have time and ultimately passed them on to a young up-and-coming botanist named Joseph Hooker at the Royal Botanic Gardens, Kew. Darwin had by then been converted to the heretical notion of transmutation that his Edinburgh professor Grant had spouted, struck by both the Galápagos birds and those amazing South American fossils he had collected. Together these presented unmistakable patterns of species’ relationships in space and time—the only explanation, he realized, was the possibility that species can change, giving rise to new species over time. Keen to see if the plants he collected told the same story as the birds, he commented to Hooker, “I hope the Galapagos plants … will turn out more interesting than you expect. Pray be careful, to observe, if I ever mark the individual Island of the Galapagos islands, for the reasons you will see in my Journal.” Hooker confirmed that the botany did indeed provide an analogous case, exclaiming that there was an “xtraordinary difference between the plants of the separate Islands … a most strange fact.”8 Darwin knew why but didn’t clue Hooker in on his transmutational thinking—not yet. But the two were to become close friends, and Darwin did eventually take the botanist into his confidence. Unlike Grant (and his own grandfather), Darwin was not a devotee of Lamarck. In October 1838, about a year and a half after becoming a closet transmutationist, he had a eureka moment that brought him to the principle of natural selection. Evolutionary change, he realized, was not so much a linear succession of species, but rather like a branching and rebranching tree—an appropriate metaphor given the importance of botany in his thinking.
Down House, Darwin’s home in Kent. Wood engraving by J. R. Brown, courtesy of the Wellcome Collection
From the get-go, botany was an important part of Darwin’s growing database, providing lines of evidence in support of his still-secret theory of “descent with modification,” as he described it, by natural selection. He and Emma Wedgwood were married in 1839, and after a two-year residence in London, the young couple moved to the country. They found just the place in the village of Downe, a handsome home called Down House, with plenty of room for a growing family—and growing gardens—surrounded by fields, meadows, and woodlands. All of these were sites for Darwin’s botanical investigations: plant geography, ecology, hybridization, pollination, and more were on the research agenda. He even got into field botany, identifying plants with the help of Catherine Thorley, the children’s governess. In 1855, he wrote Hooker celebrating his successes, “I have just made out my first grass, hurrah! hurrah!” and admitting, “I never expected to make out a grass in all my life.”9
It was in those years, especially, through the 1850s leading up to Origin, that Darwin first really got into doing his “fools’ experiments”—curious and often quirky studies that might have seemed to the casual observer like the random enthusiasms of a doddering naturalist. Once, he plucked an artificial flower from Emma’s bonnet and planted it in the garden to see if bees paid any attention to it. He also dunked ducks in tanks of duckweed to see if the diminutive plant really would stick to their backs, netted clovers to keep bees from getting to them to compare the resulting seeds with those visited by bees, minutely mapped the pollinator “gangways” of flowers, and put seeds in jars of saltwater to simulate floating at sea, periodically planting batches of them to gauge how long they could survive (and therefore how far they could be carried by currents, to populate remote islands). Then there was that memorable time he tried to “feed” clippings of his toenails to sundews. Odd and amusing, yes, but also highly informative.1
Darwin had by this time taken Hooker into his confidence, followed by two other friends, geologist Charles Lyell in Britain and botanist Asa Gray in America. He had started to pull it all together into a book, a big book that he called Natural Selection. But he was taking his time and might have continued indefinitely working on it and collecting evidence to back up the theory had he not been scooped by naturalist and fellow Briton Alfred Russel Wallace. Thirteen years younger than Darwin, Wallace was then collecting and exploring in the Malay Archipelago (mainly modern Indonesia), where he had been hard at work trying to solve the mystery of the origin of species himself. He had his own eureka moment in February 1858, discovering natural selection just a few years after his arrival in the east. By a quirk of fate, he had been casually corresponding with Darwin, and each knew that the other was interested, in a general way, in the nature of species and varieties. Wallace wrote out his newly discovered theory and mailed it off to Darwin, of all people, who (needless to say) was broadsided and devastated. Darwin’s friends came to the rescue. Hooker and Lyell quickly arranged to present some of Darwin’s unpublished writings on the subject together with Wallace’s paper. Darwin wrote Wallace, explaining that he had been working on just that theory for nearly twenty years. Now he was under the gun to come out with his book and prove his priority. But his big book was too big and would take way too long to finish. He ultimately condensed his original book down to an “abstract” of nearly 500 pages (!) and published his “one long argument” as On the Origin of Species. Wallace was taken with the book, deeply impressed and exceedingly gracious about the turn of events.2
After publication, Darwin forged on ahead, continuing work on subjects that further illuminated the principles laid out in Origin. He decided to start with orchids for three reasons.10 First, he had already been studying them and found their intricate structural adaptations for pollination just astounding, “as varied and almost as perfect as any of the most beautiful adaptations in the animal kingdom.” He had written Hooker in a state of orchidelirium, making just this point: “Have pity on me and let me write once again on Orchids for I am in a transport of admiration at most simple contrivance, and which I should so like you to admire. How I wish I was a Botanist.”11 (As if!) Second, he said, the exquisite adaptations of orchids function to ensure cross-pollination and do so with amazing precision, underscoring a point he made in Origin that at least occasional crossing was practically a universal law of nature. Finally, some had criticized Origin for lacking the reams of supporting evidence that such a startling theory demanded. Darwin had stressed that the book was an abstract, after all, but the criticism still stung, and he intended to prove that he did indeed have more evidence, stating, “I wish to show that I have not spoken without having gone into details.”
But there was more to Darwin’s orchid research than quieting his critics. Though they achieve the same end—enforcing cross-pollination by affixing pollen packets, called pollinia, to insect couriers—the intricate adaptations of orchids are not all the same. Different orchid groups accomplish pollination in different ways, and there was no single “perfect” adaptation that a creator may have made; rather, they represented variations on a theme—more consistent with the vagaries of evolutionary change than with divine design. Asa Gray was supportive and began to understand Darwin’s goal. “Of all the carpenters for knocking the right nail on the head,” Darwin wrote admiringly to Gray, “you are the very best: no one else has perceived that my chief interest in my orchid book, has been that it was a ‘flank movement’ on the enemy. … It bears on design—that endless question.”12
Darwin’s study at Down House, complete with experimental plants. Wood engraving by A. Haig, courtesy of the Wellcome Collection.
In fact, all of Darwin’s botanical works were “flank movements”—they were all of a piece: demonstrations, applications, and extensions of his theory designed to back up and reinforce his arguments for evolution by natural selection. And along the way, he made more than a few contributions to the understanding of plant biology. He demonstrated the digestive physiology of carnivorous plants, for example, elucidated the function of heterostyly (flower morphs with different stamen and pistil lengths), discovered “circumnutation” (a term he coined for the repetitive circular motion of growing shoots and searching tendrils), mapped the intricate pollination mechanisms of orchids and other flowers, and on and on. This is not to say that Darwin always got it right in the modern view—such is the nature of scientific inquiry that he sometimes barked up the wrong tree, like when his tendency to emphasize the animal-like qualities of carnivorous plants led him to believe that these plants have a nervous system of sorts. Similarly, his pioneering research into plant movement could only go so far without an understanding of plant hormones, not discovered until much later by plant physiologists. At a time when laboratory science was becoming highly professionalized, Darwin was derided by some scientists for his amateurish “country house” experiments, which lacked the controlled conditions and precision instruments of a proper lab. Sure, there is some truth to that charge, but there is also no denying that Darwin made discoveries through his home-spun experiments that proved foundational to modern studies of plant physiology, ecology, and evolution.
Darwin didn’t do it alone, of course, as he readily acknowledged. First, he knew he stood on the shoulders of such botanical giants as Alexander von Humboldt, Augustin de Candolle, Carl Linnaeus, Konrad Sprengel, Karl Friedrich von Gartner, Sir Robert Schomburgk, Robert Brown, John Stevens Henslow, and others. What’s more, he appreciated the assistance he received from all quarters, helpers whose efforts nurtured his gardens, literal and intellectual—the botanical beauties of Down House gardens and greenhouse as well as his verdant garden of ideas. Assistance came from family, friends, and correspondents far and wide who willingly collected specimens, made observations, and lent their expertise. At home, his wife, Emma, and their seven children were ever-ready research assistants, even well into adulthood. Son Leonard recalled how their investigations had the character of both “a game of play and of a scientific inquiry; and in so far as we were at play, my father was like a boy amongst other boys.”13 Darwin’s sister-in-law Sarah Wedgwood collected plants for him, and his Wedgwood nieces eagerly made botanical observations while on holiday, writing to him, “Dear Uncle Charles, of 256 specimens of Lythrum gathered this morning from different plants, we find 94 with long pistil, 95—middle length pistil, 69—shortest pistil.”
Darwin in his Greenhouse. Illustrated London News, December 1887.
He was always effusive in his thanks. “My dear Angels!” came his swift reply; “I can call you nothing else … the enumeration will be invaluable.”14
It helped to have well-connected friends, too. Botanist Joseph Hooker, first as Assistant Director and then Director of the Royal Botanic Gardens, Kew, supplied Darwin with all manner of exotic plants from around the world for his experiments, and Daniel Oliver, Keeper of Kew’s Herbarium, James Veitch, proprietor of the Royal Exotic Nursery in Chelsea, orchidologist extraordinaire James Bateman, and botanist Alexander G. More on the Isle of Wight, among others, all helped Darwin with specimens or observations or both. John Lindley, editor of the popular Gardeners’ Chronicle, was always glad to publish Darwin’s articles as well as frequent letters requesting the help of readers with this or that observation or experiment—Darwin was the original crowdsourcer. Assistance also came from far afield—the leading US botanist Asa Gray was a friend and frequent correspondent, and Gray put Darwin in touch with able observers in the American field: businessman and botanist William Marriott Canby in Wilmington, Delaware, and the talented writer and naturalist Mary Treat in Vineland, New Jersey, both of whom are cited extensively in Darwin’s book on carnivorous plants. In other quarters of the world, Italian botanist Federico Delpino lent a hand, as did Roland Trimen in South Africa and German expatriates Fritz Müller in Brazil and Hermann Crüger in Trinidad. You get the picture—Darwin’s working method shows that science is a collaborative enterprise.
Catasetum maculatum. Lithograph, drawn by Sarah Anne Drake, for The Orchidaceae of Mexico and Guatemala, by James Bateman.
Darwin’s research on plants led to six books entirely dedicated to botanical subjects, along with some seventy-five papers. His botanical books include The Various Contrivances by Which Orchids are Fertilised by Insects (1862, 1877), On the Movements and Habits of Climbing Plants (1865, 1875) Insectivorous Plants (1875, 1888), The Effects of Cross and Self-Fertilisation in the Vegetable Kingdom (1876), The Different Forms of Flowers on Plants of the Same Species, (1877) and The Power of Movement in Plants (1880). He also discussed plants in On the Origin of Species (6 editions, 1859–1872) and The Variation of Animals and Plants Under Domestication (1868, 1875). His contributions to the Gardeners’ Chronicle began in 1841 and continued for thirty-six years, both queries and articles, in addition to articles on botanical subjects in the Journal of the Linnean Society of London, the Journal of Horticulture, and the Annals and Magazine of Natural History.
Darwin covered an astonishing diversity of plants in his far-ranging studies: 125 species of climbers, nearly 70 orchid genera, including native and tropical species, 20 carnivorous plants, more than 200 species that he experimented with for pollination and movement, and dozens of fruits and vegetables. Perusing his books, it’s hard not to be inspired to grow and observe these same plants—easy to do since so many are staples of the kitchen garden or favorite ornamentals. Watching pollinators land on flax flowers; noting the age sequence of foxglove flowers; growing common and unusual vines such as hops and passion flowers to watch how they twist and twine on supports; noticing how peanuts bury themselves in the ground as they mature, as do the developing fruits of cyclamen, twisting and turning downwards toward the soil; watching three-leaf clovers fold up on a cool night; noting the slow-motion reach of sundew “tentacles”—these observations can be made anywhere, á la Darwin, out on a walk, in the garden, on the trail, or amid the houseplants.
Darwin’s writing is detailed and extensive, perhaps a little too detailed in places, which is why we selected excerpts. There is no denying that even these can be a bit dense—but it is well worth braving his prose to be rewarded with a very good sense of his painstaking technique, those minutiae of careful observation and experimentation that lie at the heart of good science. We can credit Darwin for helping us decide which excerpts to select—he was often a bit self-deprecating and at times frankly acknowledged his overly detailed writing. For example, in sending Gray the page proofs of The Effects of Cross and Self Fertilisation in the Vegetable Kingdom for review, he included a heads-up that the text was on the dry side: “Please observe that the 6 first chapters are not readable, and the 6 last very dull.”15 Not a ringing self-endorsement. “Still,” he said, “I believe the results are valuable.”
In this volume, we present forty-five plants studied by Darwin, representing the broad range of his extensive botanical research, with enough detail in the excerpts to give an appreciation for his working method and the remarkable depth of his investigations. Collectively, our selections cover Darwin’s major botanical research threads:
ORCHIDS Although Darwin had started observing native orchids nearly twenty years earlier, it was in the spring of 1860 that he first probed two native Orchis species with the tip of a pencil to simulate the visit of an insect pollinator; the pencil played the role of a moth’s probing proboscis, neatly extracting the pollen packets by their sticky bases. Intrigued, he soon started acquiring exotic orchids from the Royal Botanic Gardens, Kew and Veitch’s nursery, and pickled flowers from Trinidad. His interest in orchids was deeper than pollination—the complex structure and intimate pollinator relationship of these remarkable flowers provided a case study in exquisite adaptation through natural selection, as different orchid groups (lineages, to him) have different floral structures modified for the same function: the kind of variations-on-a-theme pattern that spoke more of an evolutionary history than divine design to Darwin.16
CROSS AND SELF-FERTILIZATION, VARIATION, POLLINATION, AND FORMS OF FLOWERS Darwin’s interest in cross-pollination went way back to his earliest speculations about transmutation—what would become known as evolutionary change. Heritable variation was a key ingredient, through natural selection, but where did variation come from? He didn’t know, but it seemed to him that crossing, or out-breeding, was crucial for some reason. Flowering plants, in all of their wonderful diversity, became the organisms of choice for studying this question. Literally rooted to the spot, how did they find mates? They didn’t, instead enticing insect go-betweens to do the matchmaking for them. Today we take for granted the role of insects in pollination, but not so in Darwin’s day; the conventional view was that insects had little to nothing to do with pollination and fruiting. Darwin championed the work of German naturalist Christian Konrad Sprengel, who argued for the vital role of insects in pollination in his beautiful 1793 book 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). Scrutinizing flowers became a passion for Darwin, dissecting them, mapping out how insects enter and leave, noting how and where pollen is deposited, and delighting in “irritable” flower structures like the trigger-sensitive stamens of barberry or orchids that can fire off their pollen packets ballistically. He reveled in meticulously documenting the adaptive structure and function of flower after flower, studies complemented by equally meticulous controlled crosses over multiple generations to document the beneficial effects of outcrossing vs. self-fertilization. While he could not know the ultimate genetic basis of variation and how it is generated, he hypothesized that crossing in plants, and sexual reproduction generally, is all about bringing together heritable variation in endless, myriad, combinations—beneficial for the individual constitution of offspring, and providing raw material for natural selection to act upon.
In the course of his floral studies Darwin stumbled upon a curious phenomenon: short- and long-style morphs of primrose flowers, termed “heterostyly.” His Cambridge mentor John Stevens Henlow had reported these primrose flower morphs years earlier but had left it at that. Darwin became intrigued, and he performed extensive experimental crosses between and within morphs to figure out their function. After testing and rejecting his favored hypothesis, his eventual conclusion, which proved correct, was that heterostyly is an adaptation to promote outcrossing. Darwin had studied dozens of heterostyled plants, performing thousands of crosses by hand with dimorphic and trimorphic species. His data showed that between-morph pollination yields a greater abundance of fruits and seeds than within-morph crosses. Later, in his autobiography, Darwin commented that “no little discovery of mine ever gave me so much pleasure as making out the meaning of heterostyled flowers.”17
CLIMBING PLANTS The earliest record of Darwin noticing climbers comes from his time in Brazil while traveling aboard HMS Beagle, where he was impressed by the abundance of “twiners entwining twiners.” Many years later, he read an 1858 paper about vines written by Asa Gray at Harvard and asked Gray to send him seeds so he could make his own observations. Darwin had been under the weather and needed something relatively easy to study; climbers became just the thing. He grew Gray’s Echinocystis seeds and followed up with one species after another, requesting loads of plants from Kew. “I am getting very much amused by my tendrils – It is just the sort of niggling work which suits me” he wrote to Hooker. By 1863, he was “madder than ever on tendrils,” and wrote rhapsodically to Gray that tendril diversity “is beautiful in all its modifications as anything in orchids.”18 In 1865, Darwin reported his observations and experiments with some twenty leaf-climbing and tendril-bearing taxa in a lengthy paper to the Linnean Society of London—subsequently expanded to The Movement and Habits of Climbing Plants (1875). He sought in climbers the same patterns he had seen in orchids: exquisite adaptation that sheds light on evolutionary history. As he had with orchids, Darwin traced out structural “variations on a theme” in climbers, structures with a function in some groups adapted for a different function in others. He recognized five categories of climbers: hook and root climbers, which he had minimal interest in; twiners, the most “primitive” climbers; leaf climbers, with various parts of the leaves enabling the plants to scramble up supports; and tendril-bearers, with their remarkable climbing abilities described in great detail. He documented circular motions traced by twiners and tendrils, noting the timing of their movement by using a visual marker to track their progress—work that led him to coin the term “circumnutation” for the elliptical movement of plant tendrils and growing shoots. Beyond adaptive structure and function, Darwin was struck by the animal-like qualities of climbers—he marveled at their touch sensitivity, and clear ability to “see” light and shadow and move accordingly. The sensory perception of climbing plants was yet another evolutionary lesson for Darwin: a fundamental link with animals, he was sure.19
INSECTIVOROUS PLANTS Poorly understood in Darwin’s day, carnivorous plants are the subject of his third botanical book. His investigations started when he came across sundews by chance while on summer holiday near the coast and he carried a few back to the family’s rental cottage for closer scrutiny. His attention snared as surely as an insect, he started growing sundews in his greenhouses, experimenting with simple techniques such as touching the dew-tipped “tentacles” on the leaves with a camel-hair brush and sprinkling countless tidbits onto the leaves to see what they would and would not respond to. Like climbers, here was another group with clear animal-like qualities. He carried out extensive studies of their “behavior,” assisted by observers abroad, including naturalist Mary Treat in New Jersey, who sent detailed observations of sundews and Venus fly traps and helped conduct experiments on the dietary preferences of these most animal-like of plants. His fascination with those qualities, not least the astonishingly fast snap-trap action of Venus fly traps—“the most wonderful [plant] in the world”20—led Darwin to team up with physiologist John Burdon-Sanderson to investigate if these remarkable plants had a nervous system of sorts.
PLANT MOVEMENT Convinced as he was of common ancestry of plants and animals deep in evolutionary time, Darwin became ever more interested in the other seemingly animal-like qualities of certain plants. His work on climbers grew into an interest in plant movements in general, and he and his son Francis launched into a series of investigations on mechanisms of movement in various plant parts—shoots, stems, leaves, or tendrils—and their context, for example, movement in response to gravity (gravitropism) or light (phototropism) and the nocturnal “sleep” movement of shoots and leaves (nyctinasty). Here was yet another case study in evolutionary variations-on-a-theme; all these forms of movement, Darwin realized, represent modifications of the slow, circular movement, circumnutation, found in all growing shoots. These studies inspired pioneering experiments on the sensory perception of embryonic shoots (the coleoptile) and roots (the radicle) by the father and son Darwin team, anticipating the discovery of plant-growth hormones and cell signaling decades later.
The movement experiments gave Darwin an even deeper appreciation for the animal–plant link, and he declared “there is no structure in plants more wonderful … than the tip of the radicle,” comparing it to a brain from “one of the lower animals.”21 Over a lifetime of study in his literal and figurative garden of botanical marvels, each of Darwin’s discoveries thrilled and delighted him in turn, each exciting wonder and inspiring his admiration to ever-greater heights. It is no surprise that he should find this, the last of his major botanical investigations, to be the most amazing yet.
Primula acaulis. Hand-colored engraved plate from Flora Londinensis, published by William Curtis.
Ipomoea nil. Bodycolor on vellum, painted by Jan Withoos, Dutch Florilegium.
Although Darwin lived in a golden age of botanical art and illustration, with paintings and engravings adorning many a book—the more lavish ones supported by subscribers and wealthy patrons—he did not make use of the fine work done by the celebrated artists of the day in his own books. Rather, Darwin preferred detailed woodcut illustrations for his botanical works, beginning with remarkable illustrations of dissected flowers for his orchid book by George B. Sowerby (who then taught Darwin’s sons George and Francis how to draw them) carved into woodcuts by Mr. Cooper. Darwin was probably not interested in attractive illustrations for his books—most of the time not even showing the whole plant, or even entire flowers—because he saw them as narrowly focused scientific tomes. We seek to remedy this deficiency.
Botanical illustration is an exquisite synergy of artistic and scientific practice, in which plants are depicted not only with great accuracy but also with a refined aesthetic that captures their beauty. Flowers and plants have always found a place in art from civilizations all around the world, but in Europe, classical knowledge was revived during the Renaissance with a new focus on the medicinal properties of plants—in the late fifteenth and early sixteenth centuries, previously symbolic representations of plants in herbals and books of hours were transformed into elegant lifelike reality by artists such as Leonardo DaVinci (1452–1519) and Albrecht Dürer (1471–1528).
In the seventeenth century, new interest in horticulture and the uses of plants stimulated further refinement of botanical art. Explorers encountered many species that have commercial value in horticulture, and plant hunters were dispatched around the world by enlightened and wealthy patrons to bring home exotics to enrich their gardens and landscapes. Arrivals in Europe of exotic plant species from Africa, the Far East and the New World, especially to Spain, Holland, and France, created new demand: discoveries and beauty needed to be captured through visual representation. Introductions of new plants gathered even more momentum in the eighteenth and nineteenth centuries with Britain’s expansion of its colonial territories.
The explosion of botanical exploration through the centuries brought opportunities for artists to capture the form and beauty of new discoveries in florilegia and scientific treatises. Multiple-volume journals and large format books were produced, illustrated by legions of exceptional artists and made available by talented professional engravers and printers in the form of sumptuous color plates. A culture of patronage brought great success for many artists, authors and publishers, as popular and unusual plants—tulips, carnations, orchids and more—were captured on paper and vellum. Artists also illustrated native plants, creating sketchbooks and floras of local species.
As new plants from around the world were being collected and studied, the desire for knowledge about plants and their properties transformed medicinal botany into a new science focused on the sheer variety of the plants themselves. The study of plant form also took on new significance as a basis for new systems of classification. The “sexual system” developed by the Swedish botanist Carl von Linné required careful observation of the parts of flowers and was popularized by the illustrations of Georg Dionysius Ehret (1708–1770), one of the most impressive and prolific of eighteenth-century botanical artists. Based in London, Ehret produced work for many publications while also teaching and inspiring others. In Paris, Pierre-Joseph Redouté (1759–1840) continued the traditions of illustrious predecessors, such as Nicolas Robert (1614–1685), and achieved great success with his paintings of roses, lilies, and much else for the French elite. In the era of Ehret and Redouté, countless other brilliant and skillful artists were in great demand, especially in England, to support the burgeoning bibliographic production.
Coincident with the upsurge in demand that flowed from the interests of artists, gardeners, and scientists, the production of books and the dissemination of botanical art was revolutionized in the late 1700s and early 1800s with the invention of intaglio printing and the engraving and etching of copper plates. The resulting prints, often embellished by hand-coloring, adorned the books collected by wealthy patrons. In the mid-nineteenth century, lithography became a prominent publishing technique, followed by chromolithography. As a result, as the demand for art in scientific works continued to grow, publication became more available and affordable. Many leading botanists from this era were themselves accomplished artists—for example, William Jackson Hooker and his son Joseph Dalton Hooker, the first two Directors of the Royal Botanic Gardens, Kew—but they also employed a new generation of superb illustrators, including Walter Hood Fitch, who worked for both Hookers. And while many captivating plant portraits were specifically created for books and journals, many artists, both amateur and professional, created beautiful originals that were saved in sketch books or bound into unpublished manuscripts.
Through a combination of demand and technical advancement, botanical art reached its zenith during the nineteenth century, coincident with the life and work of Charles Darwin. Through his studies at Edinburgh and Cambridge, his voyage on the Beagle, and his extensive networks, Darwin gained an unusually broad knowledge of plants from many parts of the world. Later, living close to London and with strong connections at the Royal Botanic Gardens, Kew Darwin certainly had access to extraordinary works of art, and perhaps perused accurate depictions of the many plants that intrigued him. Yet Darwin included very few images in his books. Curious to see what botanical paintings would have been available during Darwin’s time, and the great range of plants to which he potentially had access, we undertook the enjoyable task of gazing on his behalf upon some of the greatest botanical art of all time, especially through the unusually comprehensive collection in the library of Oak Spring Garden Foundation.
In the spirit of encouraging an appreciation of the art of Darwin’s botanical science, it is appropriate to also encourage an appreciation of his subjects and of botanical art itself. Drawing upon the stunning botanical painting and print collection of Oak Spring Garden Foundation, we bring these complementary art forms together here for modern readers. We hope that doing so fosters an appreciation of the beauty of some of Darwin’s favorite plants as well as the beauty of the scientific insights they yielded in the admiring hands of that inveterate “experimentiser.”
Cyclamen europaeum (= purpurascens). Water and bodycolor on vellum by Georg Dionysius Ehret, in Flowers, Moths, Butterflies and Shells.
Angraecum sesquipedale. Chromolithograph from Frederick Sander, Reichenbachia.