Darwin's book Climbing plants was published in 1865, but its gestation began much earlier. The start of Darwin's work on the topic lay in his need, owing to severe bouts of illness in himself and his family, for diversions away from his much harder book on species, eventually published as The variation of animals and plants under domestication in 1868. In 1862 he had read a 'Note on the coiling of tendrils' (Proceedings of the American Academy of Arts and Sciences, 4 (1857-60): 98-9) by the Harvard botanist Asa Gray. This brief paper sparked his interest, and he told Gray, 'I shd. like to try a few experiments on your Tendrils; I wonder what would be good & easy plant to raise in pot'. Gray immediately sent seeds of the two plants he had himself used to make his observations. He wrote, 'I send you seeds of one native weed which corrupted by bad company-is as nasty and troublesome as any I know, viz. Sycios angulatus, [Sicyos angulatus; bur cucumber]-also of a more genteel Cucurbitacea, Echinocystis lobata [wild mock-cucumber](the larger seeds). Upon these, especially upon the first, I made my observations of tendrils coiling to the touch'.
Darwin now had seeds to be planted in spring, but he returned to his work on Variation for the winter, his writing continually interrupted by his poor health. He did not lose his sense of humour, though, and told his best friend Joseph Dalton Hooker in January 1863, 'I have been trying for health sake to be idle with no success. What I shall soon have to do, will be to erect a tablet in Down church "sacred to the memory &c" & officially die, & then publish books "by the late Charles Darwin"; for I cannot think what has come over me of late; I always suffered from the excitement of talking, but now it has become ludicrous. I talked lately for 1 1/2 hours (broken by tea by myself) with my nephew & I was shaking & vomiting half the night-'
Darwin's journal for 1863 resolutely records each chapter of Variation as he finished writing it, but makes no mention whatsoever of work on 'Climbing plants'. His letters tell a different story, though. In June 1863, Darwin reported to Gray that although the seeds of Sicyos failed to germinate, he had already noticed something regarding the tendrils of Echinocystis beyond what Gray had reported about their sensitivity to touch, or irritability: 'I am observing the plant in another respect, namely the incessant rotatory movement of the leading shoots, which bring the tendrils into contact with any body within a circle of a foot or 20 inches in diameter'. Darwin's enthusiasm at this early stage of his research is evident; he promised Gray, 'If I can make out anything clear about this movement, & do not find that it is known, I will perhaps write a letter to you for the chance of its being worth inserting in Silliman or elsewhere' (The American Journal of Science and Arts was commonly known as 'Silliman's journal' after its founder, Benjamin Silliman). Only a week later, Darwin told Hooker about new observations made on the tropical vine Cissus discolor that Hooker had sent from the Royal Botanic Gardens at Kew. He concluded, 'I hope I have not bored you with these details. Perhaps some day I will write a little paper on these movements'. Clearly, the seeds of another 'interruption' to Variation were well and truly planted.
'Wonderfully crafty & sagacious'
While Darwin fretted over what he referred to as his 'compiling work' (Variation), a major worry being 'not knowing what to trust', he admitted, 'I am getting very much amused by my tendrils- it is just the sort of niggling work which suits me & takes up no time & rather rests me whilst writing'. At this early stage in his research, Darwin seems to have relied only on Gray's brief notice. This might have been due to Hooker's comment that Darwin's 'most curious & important' early observations, which went 'a long way towards explaining the secondary causes which result in tendrils seeking & finding', were, as far as he knew, 'the first step in that direction-' In any case, this proved fortuitous, because Darwin had made a great number of observations and experiments before looking at any of the existing literature. He recalled, 'My observations were more than half completed before I became aware that the surprising phenomenon of the spontaneous revolutions of the stems and tendrils of climbing plants had been long ago observed by Palm and by Hugo von Mohl, and had subsequently been the subject of two memoirs by Dutrochet.' Had he started by reading the works of these three authors, Darwin might have given up on climbing plants, thinking he had little to add. In fact, what Darwin brought to this research area was his underlying sense that the theory of evolution by natural selection would be instrumental in explaining the morphology and physiology of climbing in its many forms.
Asa Gray was soon to disabuse Darwin of the notion that his initial observations were new. He promised to send fresh seeds, but added, 'Rotary movement of end of tendril-bearing stems is common, is it not, and well known?' Nevertheless, he added, 'Any notes you will give me to put in Sill. Journal, I shall ⟨alw⟩ays delight in'. Hooker was always encouraging, sending more plants and noting that Darwin was '"facile princeps" [easily the best] of observers'. Darwin was now beginning to focus on the differences in tendrils of different plant families and different kinds of tendrils. He told Hooker, 'As far as I have seen, little as yet, leaf-tendrils are sensitive but have not spontaneous movements, like tendrils of Cucurbitaceæ & Viniferæ'. To his son William he enthused, 'My hobby-horse at present is Tendrils; they are more sensitive to a touch than your finger; & wonderfully crafty & sagacious'. This statement was not entirely tongue-in-cheek; as he received more climbers, he marvelled at the variety of movement in each new specimen, exclaiming that this dispelled the mistaken old view 'that animals moved & plants did not'.
Plant movement, however, could be puzzling, and determining precisely what was moving was not straightforward. Darwin complained, 'I see Henslow says tendrils of Cucurbitaceæ are stipules Gray branches, & Thomson leaves-: what is a poor devil to believe?' Hooker replied that Charles Naudin 'proves them to be foliar in the opinion of most readers, but I have no opinion of my own'. By the beginning of August 1863, Darwin reported to Gray, 'my present chief Hobby-horse I owe to you, viz tendrils; their irritability is beautiful, as beautiful in all its modifications as anything in orchids', but, he continued, 'About the spontaneous movement (independent of touch) of the tendrils & upper internodes I am rather taken aback by your saying "is it not well known?" I can find nothing in any book which I have: neither Hooker nor Oliver knew anything of these movements'. Darwin went on to describe in detail some of his observations and pleaded, 'Pray tell me whether anything has been published on this subject: I hate publishing what is old; but I shall hardly regret my work, if it is old, as it has much amused me'.
'Not knowing what is known'
Gray was incredulous. 'As to tendrils, What are Hooker & Oliver (the latter a Professor too) about, and where have they lived not to know anything of them', he exclaimed, before pointing out the references in his own short notice and adding that Darwin should 'consult Mohl (who is worth all Germany besides)'. Mohl's work had been translated into English, thanks to Gray, although as he grumbled, 'you English pay no attention to it, when you have got it'. Botany in England was still overwhelmingly focused on taxonomic studies; Hooker and George Bentham were only at the beginning of their decades-long project, Genera plantarum, and floras of various parts of Britain and its colonies generally focused on systematics or geographical distribution. Physiological botany had hardly made an impression, but in Europe, especially in Germany, the laboratory was rapidly emerging as the site of the most innovative work.
Around August, Darwin evidently decided that the subject of climbing would be worth more than a brief notice or even a short paper and now delved into the literature, most of which was from the Continent. He admitted to Hooker, 'It troubles me much not knowing what is known'. To Falconer he revealed, 'I have managed to do this summer a fair share of work and have been greatly interested by the spontaneous movements and irritability of tendrils and twining plants; but only a little of my work is new'. As he read and experimented more, however, Darwin began to identify lacunae in the work of his predecessors. He told Hooker, 'Though Dutrochet has published the cream of my work, I have been going on at Tendrils &c; for the subject has interested me much, & Dutrochet left something undone. So do not forget me, if you notice at Kew any plant with odd tendrils'.
'A broken-down brother naturalist'
As the summer of 1863 drew to a close, Darwin's bouts of sickness became almost constant and nearly all work, especially that on Variation, became impossible. His Journal recorded a six-week trip to Malvern Wells from 2 September with the gloomy comment, 'Ill, there.- Ill to end of year'. The next year brought no respite. At the end of January 1864, he told Hooker, 'The only approach to work which I can do is to look at tendrils & climbers, this does not distress my weakened Brain- Ask Oliver to look over enclosed queries (& do you look) & amuse a broken-down brother naturalist by answering any which he can'. He followed this with several questions and comments on the nature of tendrils and wishfully remarked, 'Every thing wd go very beautifully for me if botanists wd let all tendrils be modified leaves'. Daniel Oliver, for example, insisted, 'Botanists have no choice but to regard some tendrils as leaf-, & others as stem-formations', leading Darwin to counter, 'It is very strange that tendrils formed of modified leaves & branches shd. agree in all their highly remarkable properties'.
Having become familiar with climbing in its many forms, Darwin then attempted to explain climbing as an adaptation. He appeared to have given up the idea of a longer paper on the subject in spite of his friends' encouragement. 'I fear you greatly overrate the interest of my facts on climbing', he told Hooker in late February 1864, 'but I could not draw up a paper to save my life'. A week later, however, he wrote Asa Gray, 'It is now six months since I have done a stroke of work; but I begin to hope that in a few more months, I may be able to work again.- I am able most days now to get to my Hot-house I amuse myself a little by looking at climbing plants.' He optimistically stated that he planned to write up the results of his recent work.
By March 1864, Darwin was pursuing the question of which modified part the tendrils in different plant families were derived. His son William had noticed what appeared to be an incipient flower bud at the tip of a passionflower tendril, which he was dissecting and drawing. Darwin sent William's drawing to Oliver, commenting, 'Does not this render it highly probable that the tendril is a modified flower with its peduncle?' Oliver replied with a highly philosophical rumination on the 'ideal leaf', and the morphologically 'essential distinction' between foliar and axial parts, which, however, Oliver admitted, sometimes 'shades off and is lost'. Nevertheless, Oliver confidently assured Darwin, 'Between however a peduncle & a branch there is no essential distinction. They are both axial.' Only days later, Oliver apologised for the tone of his previous letter ('more seemly if addressed to one of my students') and added, 'from the way in which the enquiry was put I thought there was indication of doubt upon one or two matters which routinists regard in the light of axioms'. Darwin quickly assured him, 'I greatly prefer being treated as what I am[:] quite ignorant of the rudiments of botany'.
'New sort of work'
By late spring, armed with a good knowledge of the literature, Darwin continued to share new and increasingly astute observations with his friends, causing a worried Hooker to chide, 'I wish you would soon publish a note on tendrils &c, or you will certainly be cut out by some foreigner:- A few lines to the Gard Chronicle would suffice'. Darwin replied, 'You quite overrate my tendril work & there is no occasion to plague myself about priority', before adding, 'By the way I observed yesterday an odd little fact, that in the vine the Flower buds are borne on a true tendril, for the whole mass of flowers steadily revolves'. Throughout May and early June 1864, Darwin expanded his work, asking friends for more and different specimens and requesting that they observe plants outside his own reach. By mid-June, he told Hooker, 'I have now read two German books & all, I believe, that has been written on climbers, & it has stirred me up to find that I have a good deal of new matter'. He told Oliver that Mohl, despite his book being 'very useful', had 'overlooked much & made many mistakes'. Moreover, Mohl had 'discussed homologies largely'. As Darwin later explained in Climbing plants, 'he who believes in the slow modification of species will not be content simply to ascertain the homological nature of different tendrils; he will wish to learn, as far as possible, by what steps parts acting as leaves or as flower-peduncles can have wholly changed their function, and have come to serve as prehensile organs' (Climbing plants, pp. 110-11).
Climbing plants, p. 71
Having finished a paper on 'Three forms of Lythrum salicaria' in June, Darwin told Hooker, 'I keep on improving & am now much as usual, except that anything which is hard to understand or which hurries me, knocks me up.-As soon as I have done about climbing plants I shall resume my routine work'. Having at last stopped dithering about whether to write up the results of his observations, Darwin settled into a routine. By mid-July, he told Hooker, 'I do an hour or two's work daily at my climbers & hope in a month to finish-' As was typical of him, however, Darwin could not resist continuing to experiment and request more plants and observations from his friends. He now had his own tropical pitcher plant (Nepenthes) in his hothouse, but asked Oliver to 'observe this one point.- whether a leaf with a pitcher has ever fairly & closely wound round a stick or support'. A couple of weeks later Hooker confidently reported, 'Nepenthes climbs famously by the stalk of the pitcher & the pitcher fully develops after the process-it also thickens'.
Darwin continued to receive new plants even as he reported at the end of August 1864, 'Thank Heaven I have finished (first time over) my Climbing Paper'. He promised Hooker soon after, 'now I must & will stop looking at fresh things', but that vow didn't last long. In early October, he announced to Hooker, 'How often I have said I wd. give no more trouble about Climbers, & now again I say it is over', but by the month's end he confessed to Gray, 'I have not been able to resist doing a little more at your God-child my Climbing paper or rather in size little Book, which by Jove I will have copied out, else I shall never stop. This has been new sort of work for me & I have been pleased to find what a capital guide for observation, a full conviction of the change of species is' In December, having finished writing at last, Darwin told Hooker, 'I have just read through my gigantic paper on Climbers & am pleased with it; but Heaven knows whether it is really good.'
'Ashamed and disgusted at the length'
Having spent so much effort in writing, Darwin was now worried about where he could publish his opus. The Journal of the Linnean Society seemed the obvious choice, and yet he noted, 'I will first consult Bentham, whether Linn. Soc. will like expence of so large a paper with 12 woodcuts; for if too expensive for Linn. Soc. I wd send it to Royal Soc.; though I shd. prefer the former'. He added gloomily, 'But I repeat that I am ashamed & disgusted at the length of my paper'. Hooker instantly assured him, 'Bentham craves your paper however long-for the Linnean, & so do I'. A more relaxed Darwin replied, telling his friend, 'I have made their perfect gradation a very prominent point, with respect to the means of climbing, in my paper. I begin to think that one of the commonest means of transition is the same individual plant having the same part in different states: thus Corydalis claviculata, if you look to one leaf may be called a tendril-bearer,-if you look to another leaf it may be called a leaf-climber.'
Climbing plants, p. 81
Darwin's paper was long, but an excerpt from it was read by the secretary of the Linnean Society, Frederick Currey, on 2 February 1865. The response was enthusiastic, Hooker reporting, 'your paper went off extremely well last night. Currey read it well,-right well. Masters pointed out that all terete petioles had closed bundles. & Bentham said that there were interesting Legumes, uniting Nissolia with others & Aphaca, which would afford you capital means of testing your views. These last were most seductive & interesting'. Maxwell Tylden Masters wrote soon after, raising the points highlighted by Hooker, and mentioning his own investigations on 'spiralism as a teratological phenomenon'. By April 1865, Darwin was correcting proofs of the paper, but worried, 'it is so fearfully long, that no one will ever read it'. 'On the movements and habits of climbing plants' was published on 12 June 1865 in a double issue of the Journal of the Linnean Society (Botany). In spite of his worries, CD arranged to have an author's offprint separately printed by Taylor and Francis. In August, it was also published commercially by Longman, Green, Longman, Roberts & Green and by Williams and Norgate.
'Like a blind Cyclops'
Darwin's work received universal praise from botanists, other naturalists, and more general readers like Charles Kingsley, the Queen's chaplain, who enthused, 'Ah that I could begin to study Nature anew, now that you have made it to me a live thing; not a dead collection of names'. The nurseryman Thomas Rivers exclaimed, 'What patient research & watching! I am more than ever surprised at what you do & can do'. The entomologist Benjamin Dann Walsh wrote of climbing plants, 'this discovery of their sweeping circles & groping in the dark for support, like a blind Cyclops, is very astonishing'. From even further afield in Brazil, a new and important correspondent, Fritz Müller, began to supply Darwin with a wealth of observations and specimens to fill in some of the remaining questions on the nature and evolution of climbing. Müller's letters on the subject were submitted by Darwin for publication and appeared in the Journal of the Linnean Society (Botany) in November 1866. Darwin could never really let go of his beloved climbers, and by 1873 had begun preparing what would become the second edition of the book, published in 1875. It would not be long before Darwin would return to the subject of plant movement in all its forms; it was to become his last great botanical work, On the power of movement in plants. But that is another story.
