1 C. R,Darwin and J. D.Hooker: Episodes in the History of Plant Geography, 1840-1860 by Elizabeth Janet Browne A thesis submitted for the degree of Doctor of Philosophy of the University of London Department of the History of Science and Technology Imperial College September 1978 2. Abstract C R Darwin and J D Hooker: Episodes in the History of Plant Geography, 1840-1860 by Elizabeth Janet Browne In the absence of any recent investigations into the study of plant and animal distribution in the early nineteenth century, I exam- ine the themes which dominated this branch of natural inquiry. Using unpublished correspondence between Charles Darwin and Joseph Hooker, their published works, and treatises by other naturalists, I outline the establishment of biogeography from the twin roots of geology and biology. I propose that there was a distinctive manner in which natural- ists with a geological training or professional experience in that subject, such as Lyell, Edward Forbes and Darwin, regarded the topo- graphical arrangements of today's living beings. There was an equally distinctive manner in which natural historians and systematists, such as Hooker, looked at the same phenomena. The parallelism is illus- trated by a description of the way that each faction explained the problem of the origins of arctic and alpine floras, and the problem of geographically representative species. Furthermore, I explain how naturalists, and particularly botan- ists, understood the study of distribution and the way in which they analysed their data. I trace the history and the characteristic features of 'botanical arithmetic' (or the statistics of distribu- tion), and its transfer into related sciences, especially geology. These chapters reveal a hitherto unnoticed aspect of nineteenth cen- tury natural history. I close with a full exposition of Charles Darwin's extensive botanical calculations on large genera and varieties which he used to vindicate his theory of organic evolution. This is based entire- ly on archival material, as yet unassessed by historians. I des- cribe three stages in the development of Darwin's thought before the Origin of Species and discuss the discovery of a principle to acc- ount for diverging lines of evolution. This last I attribute to an alteration in Darwin's concepts following an enforced change in his arithmetical procedures in 1857, 3 Acknowledgements The research for this thesis was carried out with the gratefully acknowledged aid of a Major State Studentship from the Department of Education and Science, and the equally app- reciated support of a Keddy Fletcher-Warr Scholarship from the University of London. I would like to thank Professor A. Rupert Hall, my supervisor, and Dr Marie Boas Hall for the intellectual guidance and friendly encouragement which they have offered me throughout this period. In particular, I am indebted to them for the combined criticism which they brought to bear on the several drafts of this thesis. During trips to Cambridge I have also enjoyed the advice and hospitality of Sydney Smith and David Kohn, and I have further benefited from discussions with visiting Darwin scholars. To these, and to Mr P. J.Gautrey of the Cambridge University Library, I extend grateful thanks. 4 Table of Contents page Introduction 7 Part I Prologue 12 Chapter 1 The Problem of Arctic and Alpine Floras 18 1.1 The problem 20 1.2 Edward Forbes' explanation 24 1.3 Charles Darwin's explanation 34 1.4 Joseph Hooker and the geological approach to nature 42 1.5 Conclusions 54 Chapter 2 The Problem of Representative Species 56 2.1 The problem 59 2.2 Edward Forbes 64 2.3 Joseph Hooker 75 2.4 Conclusions 85 Part II Chapter 3 The Investigation into Biological Provinces 88 3.1 Conclusions 122 Chapter 4 Statistics in Distribution Studies 125 4.1 Botanical Arithmetic 130 4.2 Geological statistics 153 4.3 Conclusions 159 cont/ 5 Table of Contents (cont) page Part III Chapter 5 Charles Darwin's Botanical Arithmetic 1836-1857 161 5.1 Introduction 161 5.2 The question of range, 1836-1844 164 5.3 The question of aberrance and the size of genera, 179 1854-1857 Chapter 6 Charles Darwin's Botanical Arithmetic 1857-1858 194 6.1 The correction of Darwin's calculations 194 6.2 Divergence in the Natural Selection manuscript 214 6.3 The significance of large genera for selection 223 theory 6.4 Conclusions 228 Concl usi.ons 231 Notes 239 Bibliography 279 Appendix 'The Charles Darwin-Joseph Hooker correspondence: 300 an analysis of manuscript resources and their use in biography' 6 Illustrations following page Figure 1 Forbes 'On the manifestation of Polarity' in 65 the living kingdom Figure 2 Forbes 'On the manifestation of Polarity' in 65 the fossil record Figure 3 Forbes on the introduction of new genera over 71 time Figure 4 From Humboldt's Prolegomena 135 Figure 5 From H.C.Watson's observations on the Scottish 145 Highlands Figure 6 From Lacordaire 'On the geographical distribu- 148 tion of Insects' Figure 7 148 Figure 8 148 Figure 9 148 Figure 10 James Dana 'On the geographical distribution of 149 Zoophytes' Figure 11 From Alphonse Decandolle 'On fossil vegetables' 156 Figure 12 156 Figure 13 From Darwin's "B" Notebook 168 Table 1 Table of the composition of the Natural Selection 212 manuscript 7 Introduction "I know I shall live to see you the first authority in Europe on that grand subject, that almost key-stone of the laws of Creation, Geographical Distribution." Thus with an elegant compliment to his new friend Joseph Hooker, Charles Darwin praised the study of the distribution of animals and plants as a notable key to understanding nature. Recognising that this "grand subject" was more than a Baconian exercise in the gathering of facts, he roundly declared that it was, on the contrary, fundamental for determining the origins of living beings. So Darwin certainly thought that biogeography was an important study, and recent historians have not neglected this aspect of his researches. Camille Limoges and Michael Ghiselin have outlined the significance of the facts of geographical distribution' which he encountered in the Galapagos archipelago and elsewhere for the development of his ideas T about organic change. Sir Gavin de Beer, Nora Barlow, R.C. Stauffer, P.J. Darlington, Martin Fichman and Malcolm Kottler have discussed particular topics which helped or hindered his investigations, whilst other critics have described his views in more general histories of bio- geography and evolutionary biology. Yet few scholars have attempted to assess the place of biogeography in nineteenth century science as a whole. Was it as important to Darwin's contemporaries as it was to him? Did they too regard it as a "key-stone" to the "laws of creation" and did they draw from the data theories and hypotheses of the same order as Darwin's proposals? I assert in this thesis that the answer to such questions is 'yes'. I demonstrate that there was intense and widespread interest in bio- geographical phenomena, and a fully articulated set of propositions and axioms with which naturalists could attempt to explain the distribution of life. This interest was manifested in a variety of ways' and I illustrate how and why dissimilar trends of thought were generated and gradually interlaced. Using unpublished correspondence between Charles Darwin and Joseph Hooker, their published works, and treatises by other nineteenth century naturalists, I therefore study the development of bio- geography as a science. Apart from the fact that no-one appears to have previously conducted such a survey, my work is necessary because there is some tendency on the part of modern commentators to dismiss this "grand subject" as one which was virtually non-existent or practically medieval in character before 8 Darwin and Alfred Russel Wallace introduced evolutionary biology. Even Ronald Good, a noted biogeographer of our own times who has a heightened appreciation of the history of his topic, refers to the pre-Darwinian period as one of mere exploration and discovery from which the greatest achievement was only a gradual description of the world's living beings.2 Others, such as F.R. Fosberg, elaborate on this view to state that early biogeographical attempts were "undirected", atheoretical, and confined to the collection of facts about the ranges and distribution patterns of organisms. Naturalists, it is said, found these phenomena "curious" and "mysterious" in the extreme and were unable to explain them until a theory of evolutionary change was proposed in 1858 and 1859. This view makes little of the attainments of botanists, zoologists and paleontologists before and contemporary with Darwin. Of course the advent of evolutionary theory had a definite and far reaching effect on the course of distribution studies and I, for one, do not wish to minimise the importance of On the Origin of Species (1859) and The Geographical Distribution of Animals (1876) which set this science on the path which it was to follow for the next one hundred years. But the wish to -glorify Darwin and Wallace has led to a somewhat unjust and inaccurate assessment of the history of biogeography. It should be emphasised that there was a well developed discipline of plant and animal geography in existence before this intellectual landmark,a discipline which possessed clearly defined aims, a variety of methods of procedure and a number of conceptual and publishing conventions. In this thesis I describe how it had been gathering momentum since the turn of the eighteenth century when German scholars such as Karl Wilidenow and Heinrich Link first outlined the requirements for a study of "Pflanzengeographie",.and how, in the early years of the nineteenth century, other naturalists such as Alexander von Humboldt, Robert Brown and Augustin Decandolle set the high standards which later scholars were to emulate.