The aliveness of plants: the Darwins at the dawn of plant science
The aliveness of plants: the Darwins at the dawn of plant scienceP. Ayres 2008.
London: Pickering and Chatto. £60.00 (hardback). 227 pp.
The aliveness of plants is a rather awkward title to a highly readable and absorbing book. It describes the scientific and personal lives of Charles Darwin, his grandfather Erasmus and his son Francis – the principal botanical Darwins (other members of the family were interested in plants too). The impact of the Darwins' considerable works on today's plant science is also assessed. These themes together make a very appealing combination and the book has a determined but informal style that should attract an appreciative readership within and outside professional plant science. The author, Peter Ayres, is himself a distinguished experimental botanist and this may well explain his evident empathy with these highly influential men who combined theoretical rigour and originality with a strong work ethic and who backed their ideas with detailed observation, practical experiment and convincing writing. But Ayres is fascinated too by the evolving social environment in which succeeding generations of Darwins worked and by the personalities, medical troubles and family tribulations that marked their productive lives. The resulting book thus works well at several levels and fully compliments the author's previous historical book, Harry Marshall Ward and the fungal thread of death (Ayres, 2005).
Chapter 1 (‘Green Threads across the Ages: A Brief Perspective on the Darwins’ Botany') starts with well-chosen photographs of Erasmus looking robust and indefatigable, Charles looking thoughtful, staid and stolid in late middle-age and Francis as the reserved, sensitive and depression-prone character depicted so perceptively in much of the text. This short chapter has plant physiology (all three Darwins were concerned with this then-novel branch of botany), history, sociology. Its perspective feeds forward from Francis's and Charles's shared fascination with plant movements to the discovery of auxin, and from Francis's work on stomata at Cambridge on to that of his junior colleague F. F. Blackman on CO2 assimilation via stomata and the interaction with light (Blackman, 1905). It's a good start to the book, solidly based on the science, and introduces many of the main themes explored later in the book. In Chapter 2 (‘The Fortunes of the Darwins’) we see how substantial family wealth was a prerequisite for serious self-indulgence in botany in Britain prior to the professionalization of science in the late 19th century. Ayres describes this transition, starting with Erasmus, the irrepressible hobby botanist, prolific writer, poet and networker (he was a friend of Benjamin Franklin and Josiah Wedgewood), to Charles and the young Francis as gentlemanly men of letters working full time at home in Down House as amateurs, and on to an older Francis as salaried academic at the University of Cambridge. We also read how, in addition to their successes, Charles and Francis suffered personal problems that included Charles's continuing bouts of a mystery digestive illness and the death of his favourite daughter, Annie, from scarlet fever. All three of Francis's wives predeceased him, including the vivacious and popular Amy aged just 26. This chapter also summarizes Charles's five botanical books (F. Darwin, 1899), making it clear that although never claiming to be a real botanist (false modesty it seems), Charles was much preoccupied with plants following his return from the famous voyage on HMS Beagle. Chapter 3 (‘The Misfortunes of Botany’) assesses influences that slowed the development of botany and progressing into a science of causalities. These include its 18th- and 19th-century positioning as a minor cul-de-sac of medical knowledge (ironically Erasmus, Charles and Francis were all trained in medicine). Nevertheless, at the end of the 18th century Erasmus perceptively extolled the need for actual experimental work on plants with a view to practical gains. In the much longer Chapter 4 (‘Erasmus Darwin's Vision of the Future: Phytologia’), Ayres expands on these themes and establishes a continuum linking Erasmus's insights to the earlier pioneering discoveries of Stephen Hales, Priestly and Lavoisier and to subsequent agriculturally significant findings of von Liebig, Laws and Gilbert (amongst others). The stepwise uncovering of gaseous carbon dioxide, oxygen and di-nitrogen in the air and water and soluble minerals from the soil as the sources of a plant's dry mass finally leads nicely to mention of Charles Darwin's studies of carnivorous plants and their rather particular means of securing mineral nutrients. In the following chapter (‘Charles Darwin's Evolutionary Period’), Ayres tracks Charles's boyhood botanical training from that of his gardening-mad father and onto that of J. S. Henslow, his botany lecturer at Cambridge. We read that Henslow was instrumental in Charles's appointment as naturalist on HMS Beagle and insisted that, while on board, he read Lyell's new book Principles of Geology. This proposed an on-going dynamic evolution of the physical landscape and hinted at the immense age of the Earth (by biblical standards). These were two necessary foundations for Charles's still-latent ideas on biological evolution. Following the pivotal and much delayed publishing of On the Origin of Species which were finally prompted in 1859 by the intercession of Alfred Russel Wallace's closely similar views, Ayres documents Charles's increasing preoccupation with the study of plant behaviour as a means of putting experimental flesh on the underlying physiological machinery of generating variation (e.g. cross-fertilization) and achieving competitive advantage (e.g. climbing ability). The second half of the chapter and all of Chapter 6 (‘Charles Darwin's Physiological Period’) add further details to this botanical invigoration. A particular strength of these chapters is the linking of Charles's work to that of his contemporaries, something that was lacking in Charles's own writing – a shortcoming that reflected the cultural isolation of life at Down House and Charles's reliance on a circle of close friends and correspondents. His poor grasp of German may have also contributed to the gulf that opened up between Charles and the highly organized plant physiologist Julian von Sachs. All this and von Sachs's contempt for the amateurish Darwins is nicely captured in Chapter 7 (‘Charles Darwin, Francis Darwin and Differences with von Sachs’) and includes an account of von Sachs's personal snub of Francis in the botanical garden at Würtzburg. It is well known that the most enduring legacy of Charles's and Francis's work on plant movements is the notion of internal transmission of growth-stimulating signals from site of perception of an environmental stimulus to site of subsequent response, something von Sachs refused to accept on the say-so of the much-despised Darwins. This was unfortunate for von Sachs since it was experiments at Down House not at Würtzburg that led famously to the classic studies by Boysen-Jensen and F. W. Went of the plant hormone auxin using oat coleoptiles, the Darwins' favourite model system.
In the chapter entitled ‘Francis Darwin, Cambridge and Plant Physiology’ we are given an insight into how, in the late 19th century, the study of botany in British universities was escaping the shackles of descriptive taxonomy and developing a more vigorous experimental approach of its own, stimulated by the example of von Sachs and of certain London-based animal physiologists. Ayres explains how Francis became entangled with these developments but then dutifully retreated from the cutting-edge life in the capital to the insular world of Down House. Here Charles badly needed help with his mountain of correspondence, book-writing and revising of On the Origin of Species (it ran to six revised editions in 17 years). Somehow they also found time for the experiments that led to publication of The Power and Movement of Plants in 1880. We then read that only after his father's death in 1882 was Francis able to resume university life, choosing to return to Cambridge where, as a salaried academic, he set about supporting an overworked Sydney Vines, writing Life and Letters of Charles Darwin, revising two of his father's books and marrying again. Ayres also documents Francis's achievements in quantifying transpiration, measuring stomatal opening and in writing the first English-language guide to practical plant physiology. That familiar Darwinian capacity for hard work is very apparent in these early years on the staff at Cambridge.
The most sensitive writing in the book is to be found in Chapter 9, ‘Francis Darwin, Family and his Father's Memory’. Here, we learn how the sadness inflicted by the death of Francis's second wife, Ellen, and his teenage daughter Frances's subsequent depression lead to Francis resigning from his department in 1904. The roller coaster of later events is described particularly well. These include Frances's recovery from depression, her marriage and unexpected success as a poet and Francis's unlikely friendship with fellow Cambridge academic and anti-Darwinian, William Bateson. Bateson was much involved in the rediscovery of Gregor Mendel's work on inheritance. Ayres then uses these events to explore more modern ideas of the contributions of mutations, gene rearrangements during meiosis, and quantitative polygenic regulation of traits that generate character variability. This complex chapter mentions Francis Darwin's deliberations on consciousness in plants and their seeming talent for memory; the latter anticipating Anthony Trewavas's modern-day concept of plant intelligence (Trewavas, 2003). It ends with an account of Francis's third marriage and tranquil retirement in a Cotswold village, well away from the disturbances of World War I. In Chapter 10 (‘Fortune's Favourites?’) Ayres returns to the roles of pecuniary fortune and personal friendships in creating the opportunities for the Darwins to flourish. In particular, Ayres asks whether the success of Francis (and also that of his less-botanical brothers Horace, Leonard and George, and George's son, Charles G.) owes more to being descendents of Charles than to their own talents. This is brave material and there is also more than a hint that Charles owes much of the principle of his theory of evolution to the ideas of his grandfather Erasmus. Ayres also highlights how continuities of interest (e.g. insectivorous plants), traceable to boyhood influences from the previous generations, played their part in the Darwinian triumphs. In this analysis, Erasmus re-emerges as something of an intellectual giant. There is also more than a hint of historical objectivity being a casualty when overprotective family members intervened to distort the balance of attribution. This successful book ends with a masterly summing up of the botanical legacy of Erasmus, Charles and Francis (Chapter 11: ‘Where Did the Green Threads Lead? The Botanical Legacy’) and a plea for botanists of our post-genomic world to return to the Darwinian habit of exploring organ development and the responses of whole plants to factors such as drought that challenge their survival.
It has been a pleasure to review this informative, copiously referenced and thoroughly indexed book. Ayres comprehensively sums up the achievements of Darwinian plant science, successfully recreates the atmosphere of the times and assesses the personal strengths and frailties of each of the leading characters. All this is beautifully intertwined and placed in an enveloping framework of social and institutional change, and the work of forbears, contemporaries and successors. It is also enriched by modern interpretations of the physiological phenomena that so fascinated the remarkable botanical Darwins. The book is highly recommended.
E-mail Mike.Jackson{at}bristol.ac.uk
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Ayres P. Harry Marshall Ward and the fungal thread of death (2005) Saint Paul, MN: APS Press, The American Phytopathological Society. 168.
Blackman FF. Optima and limiting factors. Annals of Botany (1905) 19(old series):281–296.
Darwin F. The botanical work of Darwin. Annals of Botany (1899) 13(old series):ix–xix.
Trewavas A. Aspects of plant intelligence. Annals of Botany (2003) 92:1–20.
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