The Challenge of Carnivorous Plants: The Tipitiwitchet
THE NEW SPIRIT OF EXPERIMENTATION flourished in parlour laboratories and garden rooms, and found its way into the gossipy correspondence of colonial naturalists stranded continents apart. Arthur Dobbs, governor of New Carolina, was an adventurous gardener and naturalist who in 1750 had been the first person to publish a detailed account of the role of bees in pollinating flowers. One of his close friends and correspondents was the Quaker naturalist Peter Collinson, owner of a famous garden in Peckham, then a country village south-east of London. On 2 April 1759 Dobbs wrote to his friend with news of his own garden and the fortunes of the seeds they exchanged. It’s a chatty but excited letter, catching the feeling that the new frontiers of Empire were in knowledge as well as territory. And he adds, almost as an afterthought, a note on a local ‘sensitive’ plant he had come across in the nearby swamps:
I thank you for the cedar cones & almonds you sent me but as they were above eight months before I Received them none of them came forward … as I now Live near the sea coasts [at Brunswick] and have taken a little Plantation at the sound on the sea coast, I intend to try oranges and Lemmones, as the Palmetto Cabbage Trees thrive there, and by preserving shelters from our northwestwards can make any experi[m] ents, and want to try Dates … We have a kind of Catchfly sensitive which closes upon any thing that touches it[.] [I]t grows in the Latitude 34 but not in 35 degrees – I will try to save the seed here.
This letter, quoted in Charles Nelson’s ‘biography’ of the Venus flytrap, is the first written reference to a plant whose extraordinary behaviour would for the next hundred years unsettle received ideas about the distinctive character of plants and their place in the natural scheme of things, and eventually suggest a possible candidate for the ‘vital force’ that Romantic thinkers believed gave life to plants. Since classical times, philosophical notions of the ordering of Creation had been dominated by the concept of the Great Chain of Being, a rigid and unbreakable hierarchy, with God at the top and inanimate rocks at the bottom. In the biological part of the spectrum animals were higher than plants, and possessed of superior powers and abilities. A ‘sensitive’ plant, with powers of movement and capture conventionally believed to be the prerogatives of ‘higher’ organisms, undermined the whole concept of the Chain – at least in the eyes of theologians and more traditional scientists. But the discovery of the flytrap occurred at a propitious moment, when poets and the new generation of romantically inclined scientists were beginning to question the validity of the hierarchical model, and ask whether the distinctions between animal and plant were as rigid as had always been assumed. The debate sparked off by the flytrap had epistemological repercussions too. It put the usefulness of biological analogy – a favourite eighteenth-century mode of ‘explanation’ – to severe test. The common assumption that superficial similarities in behaviour implied similar causative processes had led to a multitude of blind alleys and astigmatic blunders. But often the intelligent use of analogy opened the way to new understandings of the way that plants lived out their lives, and this is the way it was, in the long term, with the flytrap. Flesh and grass, after all, were ultimately governed by the same physical laws.
Collinson, his appetite whetted by Dobb’s offhand announcement about the ‘Catchfly sensitive’, was eager for more information, and in January 1760 Dobbs obliged him. His description is made especially vivid by its switching between simile and closely observed detail, but it is nonetheless a classic example of the mechanistic model of a plant.
[This] great wonder of the vegetable kingdom is a very curious unknown species of sensitive; it is a dwarf plant; the leaves are like a narrow segment of sphere, consisting of two parts, like the cap of a spring purse, the concave part outwards, each of which falls back with indented edges (like an iron spring fox trap); upon any thing touching the leaves or falling between them, they instantly close like a spring trap, and confine any insect or any thing that falls between them; it bears a white flower: to this surprising plant I have given the name of Fly Trap Sensitive.
These days, this carnivorous oddity is known almost universally as the Venus flytrap, and a rare endemic of the Carolina swamps has become a mail-order novelty for conservatories and windowsill displays throughout the world. Schoolboys relish tweezering flies (dead and alive) into its spiny maws and do not find the existence of a plant which eats flesh the least bit peculiar. That it was seen as an altogether more challenging organism in the eighteenth century – intellectually exciting or morally suspect, depending on your point of view – is evident in the hunger that grew for specimens and seeds, though very few of them reached their destination alive.
In 1762 William Bartram, son of another Quaker naturalist, John Bartram of Philadelphia, paid Dobbs a visit and took some living flytraps back to his father. Shortly afterwards, John Bartram wrote to Collinson describing ‘sensitive catch-fly’ as a ‘Wagish’ plant, and relayed that it had the name of ‘tipitiwitchet’ amongst the local Native Americans. Collinson sunk further into frustration. A ‘Wagish’ tipitiwitchet sounded as if it might be a much more exotic visitor than the packets of obstinately sterile seeds and desiccated specimens he’d so far received.
Venus flytrap, the tipitiwitchet, painted in 1847, with the vulval pink surfaces of the leaf-traps rendered very realistically.
Nothing much happened on the flytrap front for another four years, until William Young, an ambitious Philadelphian nurseryman, turned up in London. Young had built up an influential English clientele, toadied to the royal family by making spontaneous gifts of seed, and was eventually invited to Court for a year, where he described himself as ‘Botonist to their Majesty’s’ (sic). But he disgraced himself by being ‘drawn into very bad Company of women’, and squandered his earnings. Queen Charlotte settled his debts on condition that Young returned to America immediately, and stayed away from Kew, permanently. So during 1767 he toured the Carolinas and collected ‘many barrels filled with plants’, including a few tipitiwitchets. Then his ambition overcame his loyal subservience and, flouting the queen’s edict, he decided to take some specimens back to England. They were packed in damp moss and survived the journey. Young sold them to James Gordon, a nurseryman friend of Collinson, and by the summer of 1768 the first live tipitiwitchets to have reached England were growing well in a London glasshouse.
At the end of August one of them came into flower, an event which caught the attention of John Ellis, another of Collinson’s friends. Ellis was a typical example of the Enlightenment’s polymorphous and influentially networked impresarios. He was a Fellow of the Royal Society, hobnobbed by post with Benjamin Franklin and Linnaeus and had a day job as a linen merchant alongside his consuming amateur passions for natural history and gardening. Straight away he commissioned a series of professional drawings of the plant, and took it upon himself to complete a full Linnaean name. The botanist Daniel Solander had already named its genus (entirely new to science) as Dionaea – ‘from the beautiful Appearance of its Milk-white flowers, and the Elegance of its leaves, [I] thought it well deserved one of the Names of the Goddess of Beauty’. The specific name Ellis chose was muscipula (meaning mousetrap, oddly, not flytrap), and he published his account – perhaps with an eye to maximum popular appeal – in a London newspaper, The St James Chronicle. The Chronicle may not have had the kudos of the Transactions of the Royal Society, but first publication is authoritative, and on 1 September 1768 the ‘Catchfly sensitive’ and the ‘Wagish tipitiwitchet’ were formally dubbed Dionaea muscipula, Venus’s flytrap (or as Charles Nelson literally translates it, ‘Aphrodites’s mousetrap’). With the hindsight of 250 years, there is already the slightest whiff that all was not as it seemed in the naming of the siren plant.
The name’s curious, almost oxymoronic linking of the Goddess of Love with a spiked gin trap tickled public imagination even further, and letters, pamphlets and engravings flew about botanical circles. Later in September 1768, Ellis wrote to Dr David Skene, describing graphically the apparatus inside the leaves:
In the expanded leaf are many minute dots in both lobes: these magnified are of the figure of a compres’d raspberry or arbutus fruit, and of a fine red colour. In these lie the sensibility of this Plant. I have called them the irritable glands of this plant; But nature has still further views in well securing the Insect, than by the lobes coming together, and the rows of Spines clasping each other. There are amid the glands on each lobe three erect spiculae, which must either run into the Insect on the closing of the lobes, or at least prevent it wriggling to and fro to effect its escape.
He then adds a note which took the puzzle of the organic order to which the flytrap belonged into hazier and more troubling territory:
Lord Moreton asked me a shrewd Question, when I shewd the drawing at the Society the day of K[ing] of Denmarks Election. Do you think Sr that the plant receives any nourishment from Insects it catches? I acknowledg’d my ignorance.
Catching and caging flies, even running them through with lances was one thing; they could quite conceivably be purposeless reflexes, or some sort of self-protection by the flytrap. But digestion of its hapless prey was an altogether more dyspeptic idea, even to the adventurous imaginations of botany’s inner circle.
What is odd about Ellis’s otherwise excellent description is the confidence with which he explains away the flytrap’s behaviour as an example of ‘irritability’. This was a popular concept amongst reductionist and analogical botanists, used to account for any otherwise inexplicable excitability in plants, as if it were an a priori property of vegetable tissue, as it is of human skin. A young Edinburgh student, William Logan Jr, who had heard Ellis lecture, wrote to him with an equally vague idea, which seemed both a credulous throwback to the world of medieval bestiaries and the Great Chain, and a glimpse into the future of biology:
Excuse me if in vanity & fullness of my heart I now enter on my own opinion viz: that there is a chain by which plants and animals are connected and that there is an Amphibious State neither entire Plant nor Animal. We have heard of Mermen & Mermaids. We have seen Sea Dogs & Sea Lyons. We have the Bat and numerous Instances in other parts of the Creation where the animal belongs to two classes. Why not then in Plants?
Intellectuals were intrigued by the existential status of the plant, and its technique in catching prey, but not many asked questions about the purpose of the fly catching. Most seemed happy to accept the model of a mechanical spring trap driven by some otherwise unexplained ‘irritability’, including Charles Darwin’s ever ingenious grandfather, Erasmus. He had seen the ‘Flytrap of Venus’ for himself on 20 August 1788 at Ashburn Hall in Derbyshire, and had drawn ‘a straw along the middle of the rib of the leaves as they lay upon the ground round the stem’ to watch them close ‘in about a second of time … like the teeth of a spring [rat]-trap’. Erasmus thought the plant’s aggressive behaviour was to protect the leaves from nibbling insects, not eat the marauders themselves. This was also, he believed, the reason behind the fly-catching habits of Dionaea’s European relative, the sundew, which holds and smothers insects by means of sticky hairs on its leaves, ‘As the ear-wax in animals seems to be in part designed to prevent fleas and other insects from getting into their ears.’
This is a footnote to a stanza on sundew (‘A zone of diamonds trembles round her brows’) in Erasmus Darwin’s preposterous but hugely entertaining The Botanic Garden, a long, florid poem – subtitled The Loves of Plants – which attempts to translate Linnaeus’s sexual system for classifying plants into a series of melodramatic tableaux, full of sylphs, swains, knights, wronged maidens and vengeful demi-gods. When he gets to Dionaea (which he also classes as a Silene) he has nothing to say about its life, but his brief couplet has an odd and probably unintentionally erotic resonance with what are now thought to be the origins of that teasing name ‘tipitiwitchet’:
The fell SILENE and her sisters fair
Skill’d in destruction, spread the viscous snare.
In December 1990 Daniel L. McKinley, an emeritus professor of biology from New York, wrote to Charles Nelson about some tipitiwitchet evidence he’d unearthed while working on a biography of William Bartram. He’d been puzzled, as have many naturalists, over this supposedly vernacular tag, and the vague suggestions by Ellis that John Bartram had reported it as an ‘Indian name, either Cherokee or Catabaw [sic] but I cannot now recollect’. What alerted McKinley’s suspicions was a throwaway remark in a letter from Collinson in June 1784: ‘I hear my Friend Dobbs at 73 has gott a Colts Tooth in his head & married a young lady of 22. It is now in vain to write to him for seeds or plants of Tipitiwitchet now He has got one of his Own to play with.’ McKinley was told by authorities from the Department of Anthropology at the US National Museum of Natural History that no such word existed in any native American language. (Since then I’ve located, via an internet search, a very similar term for the flytrap – ‘titipiwitshik’ – in a dictionary of the Lenape language of East Coast Indians. This is certainly close enough to be a prompt for the snappier and more memorable term the North Atlantic botanists’ club began to use, but it doesn’t invalidate McKinley’s intriguing theory about why they may have tweaked it.)
McKinley then tried another tack, and looked for what the word might mean in English. In Eric Partridge’s Dictionary of Slang and Unconventional English (1970), ‘tippett’ is a fur collar. This is one of the standard meanings given in the Oxford English Dictionary, too, which also gives as meaning (2), ‘a jocular term for a hangman’s noose’, and (3), ‘an organ or feature in an animal resembling or suggesting a tippet’. In other dialect dictionaries McKinley found ‘twitch’ as a noose for frisky horses, or a tight boot. ‘Twitchety’ is fidgety or jerky. Ozark mountain folk tales used the term ‘twitchet’ for the female genitalia. It begins to look as if flytrap leaves – a pair of moist, red, semicircles fringed by hairs, which remorselessly gripped their hapless prey – were being likened to the vagina dentata. Whichever member of the group originally coined the name, it looks as if he was deliberately intending it to be a piece of covert ribaldry.
McKinley also suggests that the ‘Venus’ in Venus flytrap was a respectably disguised riff on the same idea. In Botticelli’s painting The Birth of Venus, the Goddess of Love emerges – naked but demure – from a scallop, a rather flat and unsuggestive mollusc (the painting is often jokingly referred to as ‘Venus on the half-shell’). But Venus as a scientific name was proposed by Linnaeus in 1758 for a group of bivalves, including the Quahog shore clams of North America (now generically known as Mercenaria) and the Royal Comb Venus shell (Venus dione now Pitar dione), which when opened have an uncanny resemblance to the splayed leaves of a tipitiwitchet. They’re moist, semicircular, full of soft, palpable flesh, and with a powerful grip when closing. A man trap more than a muscipula.
This is all conjecture, but highly plausible, and in the end not at all surprising. This group of middle-class literati were simply adding their ha’p’orth to the long vernacular tradition of appointing bawdy names to plants, especially when there is the slightest hint of a sex organ in their appearance. (Others include bull’s bag for orchid roots, dog’s cock and jack-in-a-box for cuckoo pint.)
It’s gratifying to see this tradition still continuing, with witty contemporary grace notes. In 2006 the carnivorous plant breeder Barry A. Rice decided to dub a well-known but till that point unnamed bright green flytrap, ‘Justina Davis’. William Collinson had been over discreet in describing the seventy-three-year-old Arthur Dobbs’s bride as being twenty-two-years-old. Justina was just fifteen. Rice explained his tag: ‘The electric green leaves can be mistaken for fresh young traps that have not yet time to develop pigmentation.’ In 1968, secondary school children on the Isle of Man, acting from a kind of instinctive sympathetic magic, also saw ‘fresh young traps’ in the ensnaring leaves of sundew. In the year of peace and love, a labelled dish of the plant in the Manx Museum was pilfered by local teenagers, who slipped bits of the plant into the pockets of their crushes.
Seventy years after Erasmus Darwin had tickled the maw of Venus with a straw, and seen her snap tight shut on it, his grandson Charles became intrigued by the more decorous entrapments of Dionaea’s relative the sundew:
During the summer of 1860, I was surprised by finding how large a number of insects were caught by the leaves of the common sundew (Drosera rotundifolia) on a heath in Sussex. I had heard that insects were thus caught, but knew nothing further on the subject. I gathered by chance a dozen plants, bearing fifty-six fully expanded leaves, and on thirty-one of these dead insects or the remnants of them adhered … Many plants cause the death of insects (for instance the sticky buds of the horse chestnut (Aesculus hippocastanum)) without thereby receiving, as far as we can perceive, any advantage; but it was soon evident that Drosera was excellently adapted for the special purpose of catching insects, so that the subject seemed well worthy of investigation. There results have proved highly remarkable.
Charles Darwin was as ingenious a writer as he was a scientist. In this passage he sets up his forensic investigations with the craft skills of a country-house thriller author: the drowsy backcloth of a Sussex heath in summer, the mysterious bodies, the confession of initial ignorance, the promise of startling evidence to come. Insectivorous Plants, which progresses to the mystery of the even more murderous flytrap, is a page turner.
Sundew haunts bogs and damp acid moorland, where the soil is low in nutrients. Its most significant feature is its leaves, which, as grandfather Erasmus had noted, are round and covered on their upper surface with fine, translucent, dew-tipped hairs – ‘or tentacles as I shall call them,’ Charles writes, ‘from their manner of acting’. It is the first of many animal analogies he uses in his deconstruction of botanical carnivory. He counts the numbers of tentacles on thirty-one leaves, and finds that they range from 130 to 260. Each is ‘surrounded by large drops of extremely viscid secretion, which, glittering in the sun, have given rise to the plant’s poetical name’. They are short in the centre of the leaf, and longer towards the edge.
The problem they posed Darwin is this. When a small object is placed on the central hairs, they appear to transmit ‘a motor impulse’ to the marginal hairs, which bend slowly towards the centre until they all become closely curled around the object. Full closure takes between one and five hours, depending on the size of the object and its nature. How did vegetable tissue move purposefully to catch insects, and then go on to digest them? What set the whole sequence in motion? How was the ‘motor impulse’ transmitted through the leaf?
Over the next months (possibly years) Darwin conducted an astonishing range of experiments with sundew plants, to test their sensitivity and appetite. He tries feeding them insects, dead and alive (but is soft hearted enough to rescue a half-caught gnat), and then with much of the contents of his larder: hard-boiled egg, roast beef, milk, cheese. Then he tries splinters of glass and cinders, and a huge range of chemicals. He breathes on the leaves, and even coughs up some of his own sputum to test the limits of the sundew’s palate for organic material. He uses minute and precisely measured lengths of women’s hair, ‘weighed for me by Mr Trenham Reeks, in an excellent balance, in the laboratory, in Jermyn Street’.
His findings were exhaustive and beyond dispute. A living insect was more efficient as a trigger than a dead one, as in struggling it presses against more glands (Darwin’s name for the viscous tips of the tentacles). A gland will be excited by being simply touched three or four times, and after a while the leaf itself begins to curl inwards ‘so as to form a temporary stomach’. The leaf quickly distinguishes between organic and inorganic matter (implying some sort of chemical feedback from the digestive system which Darwin doesn’t explore), but when satisfied that its catch contains nitrogenous matter starts to pour out digestive juices. Darwin makes the point that these act in the same manner as human gastric juices, and though unable to analyse the secretions, found that they became more acidic during digestion, and contained some analogue of pepsin in their capacity to dissolve albumen. ‘There is therefore,’ he concludes, ‘a remarkable parallelism between the glands of Drosera and those of the stomach in the secretion of their proper acid and ferment.’ In analysing the digestive process he also established the link between Drosera’s nutrient-poor habitats and its insect-catching habit: the ‘advantage’ that he was unable to see at the start of his investigation was a compensation for the lack of nutrients in acidic, peaty soils. (There is an endearing aside where the Victorian dietary improver gains ascendancy over the stringent experimenter: ‘a decoction of cabbage leaves is far more exciting and probably nutritious to Drosera than an infusion made with tepid water’.)
He repeats a similar series of experiments with the Venus flytrap, with results that were comparable, but strikingly different in detail. The lobes of the flytrap’s leaves are covered with minute glands which have the ability to secrete digestive juices and absorb food. Each blade of the leaf also has three prominent filaments which are highly sensitive to touch. Darwin observed that they were selective in their response (they ignored simulated raindrops and human hairs) but didn’t realise that at least two of the filaments had to be touched within less than twenty seconds for the trap to be sprung. (A mechanism to ensure the plant doesn’t waste its energies catching the wind or insignificant prey.) When this happens the lobes snap shut in about one tenth of a second and begin squeezing the insect with such force that an impression of it can be imprinted in the lobe’s surface. The glands start to pour out digestive juices. Sometimes, when the prey is large, they will stay rigidly shut for up to ten days, and can’t be prised open without tearing the leaf tissue.
Darwin himself didn’t uncover the channel or mechanism by which the stimulus from the filaments activated movement of lobes or tentacles. He observed that there was a movement of fluids, and that waves of ‘aggregation’ moved through the activated plant. But he knew these were the effects rather than the source of the excitation that spread through the plant. He was thrilled when in 1874 one of his contemporaries, John Burdon-Sanderson, discovered that an electric potential was set up across the leaf when one of the hairs is touched. Burdon-Sanderson was a professor of physiology at University College London, and had made a study of the electrical impulses which activated animal muscles. And again the fastidious Darwin was happy to make a cross-kingdom analogy when reporting the professor’s findings, likening the lobe’s movement to the ‘contraction of the muscle of an animal’. It was to be more than a century later that the mechanism of the two-hair trigger was unravelled. Two researchers at the University of Bonn, followed by Alexander Volkov at Oakwood University in Alabama, found that the first touch of a single hair activated an electric potential, which is stored, as if in a temporary battery, by a rise in the concentration of calcium ions in the lobe. This lasts about twenty seconds and then dissipates. But if by then a second hair has been touched, another potential builds up, the cumulative charge overrides some cellular fail safe, sets off a shift of fluids in the leaf cells, and the trap snaps shut. In effect Dionaea has a short-term memory, storing information about its earlier experiences and using this to influence its future behaviour.
Not only had electric signalling been discovered in a plant, fulfilling the dreams of many eighteenth-century botanical thinkers, but also the capacity to keep and retrieve information – an attribute previously thought to be the prerogative of brains. Erasmus Darwin would have been beside himself.