Makers of British botany/Arthur Henfrey 1819—1859
Narrative—state of Botany—dawn of the Golden Age—sexuality of Angiosperms—Schleiden's elucidation of fern life-history—Nägeli, Suminski and Hofmeister—recognition by Henfrey—original work—publications—the Micrographic Dictionary—The Botanical Gazette—its features—Henfrey's labours not immediately productive.
The claim of Henfrey to rank among the founders of botany in this country depends less on his own original contributions than on a whole-hearted devotion to the propagation and diffusion of the newer methods and results which marked an epoch during the forties and fifties of last century. The outset of Henfrey's career coincided with a great turning point in the history of botany, and to Henfrey will always belong the credit of being the first Englishman to recognise the full significance of the movement. From that moment he unceasingly made known and diffused in this country the results of the German renaissance. That Henfrey should have failed to establish the newer botany in England was the result of a variety of circumstances, one of which was his early death.
The available biographical material of Henfrey being extremely meagre, it has been necessary in preparing the present account to rely almost entirely on his published writings. In some ways this lack of personal details is no disadvantage as our present interest in Henfrey depends essentially on the movement in botany with which he was identified.
Arthur Henfrey was born at Aberdeen, in 1819, of English parents. He underwent the usual course of training for the medical profession at St Bartholomew's Hospital—becoming a member of the Royal College of Surgeons in 1843. In consequence of bronchial trouble, to which he eventually succumbed at the early age of 39, Henfrey never practised his profession. Compelled to a life of seclusion he at once turned to a scientific career and more particularly to the pursuit of botany. In 1847 he undertook the duties of Lecturer in Botany at St George's Hospital Medical School, where among his colleagues was Edwin Lankester, himself a redoubtable naturalist and the father of Sir Ray Lankester, the eminent zoologist of our own day.
Henfrey succeeded Edward Forbes as Professor of Botany in King's College, London, in 1852—a post which he held till his death. He was elected to the Fellowship of the Royal Society in the same year.
He died quite suddenly in 1859, at the house on Turnham Green, where he had resided for many years.
In order to understand the part played by Henfrey, it is necessary briefly to review the state of botany in the first half of the nineteenth century.
Linnaeus of course, botanically, the outstanding fact of the eighteenth century, was no exception to the dictum that "the evil that men do lives after them."
It was supposed that botany had reached its culminating point in Linnaeus and that improvement could only be made in details elaborating and extending his system. As Sachs tells us in his History, the result was that "Botany ceased to be a science; even the describing of plants which Linnaeus had raised to an art became once more loose and negligent in the hands of his successors. Botany gradually degenerated under the influence of his authority into an insipid dilettantism—a dull occupation for plant collectors who called themselves systematists, in entire contravention of the meaning of the word."
This was written with especial reference to Germany, but it applied with no less force to our own country where the Linnaean idea had taken deep root and the Linnaean collections had found a sanctuary.
However, by 1840, a change was coming over the face of botany. Little as it can have been dreamt, the Golden Age was already beginning—destined in a relatively short time to transform the subject. This Golden Age was contemporaneous with, and immediately dependent on, the rise of a group of young botanists in the Fatherland, a group which included von Mohl, Schleiden, Hofmeister, Nägeli, Cohn and De Bary. Later it was reinforced by Sachs, who in addition to being a brilliant physiologist was a gifted writer who did much to establish scientific botany on a sound footing. It is impossible to overestimate the debt due to Sachs, particularly for his great Textbook of Botany, which at the right psychological moment brought the whole of the modern work between the covers of a single volume.
It was with the dawn of this period that Henfrey identified himself. In the 15 years of his active career (1844—1859) he devoted himself very largely to making his fellow-countrymen acquainted with the newer aspects of botany. More particularly it was the recent discoveries as to the reproduction and life history of the Vascular Cryptogams that specially engaged his interest—the researches which broadly speaking we associate with Hofmeister to-day.
Before we go on to speak of the sexuality of the Cryptogams however, a few words may be devoted to that of the flowering plants.
Sexuality of Flowering Plants. At the period when Henfrey entered on his career as a botanist no reasonable doubt remained as to the existence of sexes among the flowering plants. The theory of the sexual significance of the organs of the flower, brilliantly founded by Koelreuter in the previous century, had been perfected with a great volume of experimental proof by K. F. Gaertner the son of Joseph Gaertner of Carpologia fame.
By 1830 the mechanism of fertilisation came to light in Amici's discovery of the pollen tube which he traced from the stigma to the micropyle. The microscopic aspect of the problem was taken up with great energy by Schleiden and brought to the forefront as the burning question of the early forties. The theory of Schleiden, which applied in particular to the flowering plants, made its influence felt to such an extent in the search for evidence of sexuality among the Cryptogams, that we may conveniently state in a few words in what it consisted.
Schleiden traced the pollen tube into the micropyle, and thence to the nucellus where it depressed or invaginated the apex of the embryo-sac, and in the recess or indentation so produced the tip of the pollen tube was converted into the embryo—its actual apex being represented by the plumule. This theory was the lineal descendant in modernised trappings of the old view expressed by Morland and others at the beginning of the eighteenth century that the embryo was contained in the pollen grain, and that the ovule was no more than the brood chamber whither it must be brought to undergo further development. This erroneous interpretation of the true facts was always repudiated by Amici, and was finally overthrown by Hofmeister and Radlkofer in the early fifties. In this connection we may note in passing Henfrey's careful paper on the impregnation of Orchis Morio, published in 1856, which fully corroborated Amici. In this paper the relations of pollen tube, embryo-sac, egg-cell, suspensor and embryo were correctly interpreted, and the new point established, contrary to the assertions of previous observers, that the ovum or "germinal-vesicle," prior to fertilisation, was a naked, unwalled cell.
Sexuality in Cryptogams. By far the most important question that came to a head in Henfrey's time was that of the morphological relationships of the Cryptogams and flowering plants. Hitherto these had remained altogether obscure in the absence of reliable data based on the proper application of the microscope to the elucidation of the life histories of the lower plants. Under the influence of the Linnaean school, which had taken deep root in this country, as elsewhere, the systematic study of flowering plants had been widely pursued, and in so far as the ferns were concerned their homologies were commonly interpreted in terms of the flowering plants. Without any real guidance in fact, a great diversity of views of these homologies found expression. The following, taken from Lindley, may serve to illustrate their general nature.
The sorus was regarded as a sort of compound fruit, the sporangium as a carpel, the annulus as its midrib, and the spores as the seeds. Speculations such as these are of the same order as the crude conjectures which with less excuse relieve the answer books of examination candidates at the present time.
In the search for the male organs of the fern attention was naturally directed to the neighbourhood of the sorus, and the stomata, indusia and glandular appendages were in turn mistaken by various observers for the anthers. The "limit" was reached by Griffith who, as is stated at page 190, conjectured that the Anabena filaments which accompany the megasporangia of Azolla were no other than the male organs of that plant.
Schleiden spoke of these researches with the utmost scorn. "For my part I am surprised that no one has yet insisted upon the presence of the organs of sense, as eyes and ears in plants, since they are possessed by animals. Such an assumption would not be a bit more absurd than the mania of insisting upon having anthers in the Cryptogams, simply because they are found in the Phanerogams."
All these ill-grounded hypotheses were swept away in 1844 when Nägeli discovered antheridia containing spermatozoids on the "cotyledon" or pro-embryo of the fern—the prothallus we call it now. Nägeli at once recognised their essential agreement with the antheridia already known in the Bryophytes and compared the spermatozoids with the corresponding structures in animals. But as he overlooked the existence of the archegonia, or rather by some lapse mistook them for stages in the development of the antheridia, it is not surprising that he was at a loss to understand the significance of his discovery, and that he should have commented on his dilemma in the following terms. "Seeing that the female organs (spores) arise on the frond at a much later stage of development, and long after the pro-embryo has died away, the function of the spermatozoids is far from evident."
It was only three years later that light was thrown on the situation, and from an unexpected quarter. Count Suminski, an amateur microscopist, announced the discovery of additional reproductive organs on the fern pro-embryo, which he clearly distinguished from the "spiral filament organs" or antheridia. His full paper, which appeared in 1848, marks an epoch in morphology, and was a very remarkable performance. In it he redescribes the antheridia and spermatozoids—detecting their tufted cilia which Nägeli had overlooked. The archegonia he describes as ovules without envelopes consisting of a papilla (the neck) which becomes perforated, giving the spermatozoid access to the embryo-sac within. His figures of the process of fertilisation are extremely interesting as they show how completely he was dominated by the theory of Schleiden to which allusion has already been made. The head of the sperm is represented as entering the "embryo-sac," and there becoming encysted to form the embryo just as the tip of the pollen tube was supposed to do in flowering plants. The further development of the embryo and its various organs are traced and figured, however, in the most admirable way. At the conclusion of his paper Suminski states that in view of the presence of male organs and ovules, and the occurrence of fertilisation, the cryptogamy of ferns does not exist in a physiological sense, and ceases to have any validity as a peculiar character. A remark which he follows up by the statement that ferns must on the existing classification be referred to the Monocotyledons.
In certain respects no doubt Suminski's paper is fantastic—more especially the circumstantial details given of the process of fertilisation. But, however we may criticise his work the credit belongs to Suminski of showing (1) that sexual organs are borne on the prothallus, (2) that the embryo fern plant is produced as the result of fertilisation. Unlike Nägeli, to Suminski came the happy inspiration of looking for the female organs in the position where common sense indicated they ought to be found.
Suminski's paper instantly aroused universal interest, and the whole of his assertions were at first categorically denied by the German botanist Wigand.
We may now trace Henfrey's attitude to Suminski's work.
His first notice occurs in the body of a review of Lindley's "Introduction" in the first volume of his Botanical Gazette, and shows him to have been profoundly sceptical, if not contemptuous, of the occurrence of fertilisation in the prothallus of the fern. His words are "this (i.e. Suminski's discovery) appears to have little but originality to render it worthy of notice." That appeared in February 1849.
Writing at greater length of Suminski's work in the Annals and Magazine of Natural History, in November of the same year, he speaks much more guardedly. "These researches are in the highest degree curious, and if the facts related prove to be correct, most importantly affect the received views of analogies in the generative processes of plants."
At the same time Henfrey says he hopes to speak more definitely on this matter when his own investigations are complete. Two years later his own very careful work in the same field was laid before the Linnean Society, in which he corroborated the main facts that had come to light. Turning once again to the paper of Suminski, after making certain criticisms of detail, Henfrey handsomely remarks—"Nothing however can take from him the credit of having discovered the archegonia and their import, one of the most important discoveries in physiological Botany of modern times since it has led to results revolutionising the whole theory of the reproduction of plants and opened out a totally new sphere of inquiry into the laws and relations of vegetable life."
For some little time after these discoveries the archegonia of the fern were, on the initiative of Mercklin, commonly referred to as the "organs of Suminski," a custom which happily fell into desuetude. Mercklin, in his paper, which essentially repeats the work of Suminski, states that he devoted his entire attention for three months to the fern prothalli before he succeeded in observing the entrance of a spermatozoid.
In reviewing the early papers of the Hofmeisterian epoch—papers which form the bed-rock of the existing morphology—one is struck with the marvellous rapidity with which their significance was apprehended. We find the phrase "alternation of generations" employed within two years of the discoveries of Suminski, whilst by the early fifties the general genetic relations of the vascular series were realized in quite a new light.
As Sachs puts it:—"When Darwin's theory was given to the world eight years after Hofmeister's investigations, the relations of affinity between the great divisions of the vegetable kingdom were so well established and so patent that the theory of descent had only to accept what genetic morphology had actually brought to view."
Among Henfrey's original contributions other than those dealing with the burning questions already mentioned, was a series dealing with the Anatomy of Monocotyledons. This would appear to have led him on to study the Nymphaeaceae, and especially the anatomy of Victoria regia—a paper which may be compared perhaps with Prof. Gwynne-Vaughan's more recent study. Henfrey was quite alive to the monocotyledonous affinity, and the enlightened and, for that date, unconventional views to which he gave expression, drew an interesting notice by Hooker and Thomson in the first volume of their Indian Flora.
Another of his papers dealt rather fully with the development of the spores and elaters of Marchantia, where he filled in a considerable lacuna in the knowledge of that group. It is curious to find as late as 1855 so intelligent and well informed a botanist as Henfrey laying it down that the cells of Marchantia, in particular, and Liverworts in general, were destitute of nuclei. It is superfluous to say that this apprehension was quite baseless. Indeed, forty years later, the group of the Liverworts was deliberately chosen by Prof. J. B. Farmer, for the investigation of nuclear phenomena on account of the favourable conditions under which they could be studied!
Microtechnique at that time was of course a much simpler affair than it has since become. Contemporary papers as a rule say little about methods; however one of Henfrey's occasional notes in a magazine tells us that caustic potash, iodine, sulphuric, hydrochloric and acetic acids, together with ether were in common use. Schultze's reagent—chloride of zinc iodide—was invented in 1850, but does not appear to have been generally employed till many years later.
It would however be a serious error to underestimate the value of the earlier work in plant histology. The present writer once spent an interesting morning in Pfeffer's laboratory at Tübingen rummaging through hundreds of the great von Mohl's anatomical preparations. Among these were sections of palm endosperms in which the, at that time recently discovered, continuity of the protoplasm through the cell walls was plainly visible. The existence of these filaments had been detected by von Mohl some years before, but he had refrained from publishing his observations from over-cautiousness.
As a translator and editor Henfrey was responsible for the English edition of von Mohl's Principles of the Anatomy and Physiology of the Vegetable Cell, published in 1852, for two volumes of Reports on Botany in the Ray Society's publications, whilst he had a considerable share in Lankester's translation of Schleiden's famous Principles of Scientific Botany, 1847. In addition to these there were constant abstracts and critical reviews from his pen in the Annals and Magazine of Natural History—a journal of which he became botanical editor before the close of his life.
As a writer of text-books Henfrey was very prolific. First came his Outlines of Botany, 1847, followed by the Rudiments of Botany. Much more ambitious was his Elementary Course of Botany which became a standard text-book running through numerous editions after his death, under the editorship of the late Dr M. T. Masters. To these must be added, in conjunction with Griffith, the Micrographic Dictionary, a substantial volume dealing in innumerable special and general articles with the microscopic study of plants and animals. This work was no mere compilation, but embodied in its pages is a very large amount of independent observation. The illustrations covering nearly fifty plates were by Tuffen West, and reached a high degree of excellence. A well known botanist, a contributor to the present volume, has more than once assured me that it was to the Micrographic Dictionary that he owed his salvation!
Should anyone desire to get a vivid and accurate picture of the precise state of Botany in this country at the middle of the last century, he cannot do better than turn over the pages of The Botanical Gazette, a monthly journal of the progress of British botany, founded and conducted by Henfrey. It was about the size of our own New Phytologist, with which it had not a little in common. In one respect it differed; unlike the New Phytologist the Gazette was financially a failure and after carrying it on at his own expense for three years (1849—1851) Henfrey had to relinquish the undertaking.
A perusal of its contents clearly shows that its editor regarded his journal as one of the instruments of diffusing the New Botany. Having to rely largely for his subscribers upon the amateur collector he points out in the prefatory note that a feature will be made not only of home botany but also of contributions or abstracts from abroad dealing with floras which have much in common with our own. For the benefit of those whose collections had reached considerable dimensions, and for whom the lack of new plants might connote a waning stimulus, he held out the further inducement of papers on the general anatomy of familiar plants, of which an excellent example by Thilo Irmisch on the stolons of Epilobium was included in the first number.
For the three years of its existence Henfrey kept faith with the British botanists and a number of The Botanical Gazette rarely appeared without an article contrived for their edification. The task was evidently a congenial one, for Henfrey had a sound knowledge of British plants with especial reference to geographical distribution and critical forms. Unlike several later exponents of the New Botany, Henfrey was quite able to hold his own with the systematists. He more than once expresses the opinion that there was too great a tendency to lump species in the handbooks to the Flora, and he urged on the occasion of the preparation of the third edition of the London Catalogue of British Plants that many more forms should find recognition. The editors of the catalogue however successfully opposed the suggestion on the ingenious grounds that it would raise the weight for postage beyond the limits of a blue (twopenny) stamp!
Henfrey thought much might be done by cultivation under varying conditions to settle vexed questions as to critical species, and suggested that a limited number of botanists in different parts of the country should co-operate in a scheme under which seed should annually be distributed, harvested and re-distributed among those taking part. Henfrey himself offered to undertake the somewhat onerous duty of receiving and distributing the seed and of generally correlating the work. As however his proposal was merely tagged on to a note on Sagina apetala and ciliata it is hardly remarkable that nothing came of it.
An interesting minor feature of the Gazette was the reporting of the proceedings of the various Botanical Societies throughout the country. These show that a chronic state of intellectual famine frequently obtained even at the leading societies—a state of which vestiges are still occasionally discernible. It was no unusual occurrence at the Linnean even during the period of Robert Brown's presidency for the meeting to be regaled with long extracts from the commentaries on the Hortus Malabaricus. In this respect however the record was easily held by the now defunct Botanical Society of London, which eked out its programme for a whole year with a communication by a Mr D. Stock "On the Botany of Bungay, Suffolk." Begun on the 11th October, 1850, it only drew to a conclusion on the 3rd October, 1851. There were other attractive features in The Botanical Gazette on which space does not allow me to dwell.
The general impression gained, however, from a perusal of the papers of that time is that they were refreshingly short, as compared with our own day, and often very much to the point. The recording of observations was rarely made the occasion for a survey of the whole field of botany, and little trace was discernible of the present habit of over-elaboration.
The foregoing outline of Henfrey's activities shows that they were devoted wholly to the spread of the Newer Botany in this country. The means employed included the publication of reviews and abstracts, the editing of translations of the more notable books, the founding of journals, and the writing of text-books. Moreover by his own investigations he kept close touch with the modern work and was indeed the means of corroborating and often materially advancing many of the larger problems before putting them into general circulation in this country.
And yet, in spite of this complete devotion of his life to the cause, the New Botany found no permanent place in this country till twenty years after Henfrey's death.
Botanically speaking, the organisation and rise of taxonomy was the ruling pre-occupation of the period under consideration, a direct outcome of colonial expansion and consolidation. Fed on unlimited supplies of new material from the ends of the earth the taxonomic habit became supreme. What could an isolated student and recluse like Henfrey do to stem this flood? Circumstances were too strong for him, and founding no immediate school it remained for a later generation to take up the task.
Though the history of the establishment of the New Botany in England lies outside the province of this lecture, it is instructive, as a contrast in methods, to note the manner of its accomplishment. Henfrey, who relied on his pen, had proved ineffective to bring about a revolution. Twenty years later it fell to Sir William Thiselton-Dyer, then a young man, to succeed where Henfrey had failed. By his enlightened teaching and personal magnetism, Thiselton-Dyer aroused a widespread interest in laboratory botany. But the matter was not allowed to rest there. Holding as he did an important post at Kew, the strategic centre, he was able to obtain appointments in the chief Colleges and Universities of the country for the recruits whom he had attracted. In this way, by the exercise of an acute intelligence amounting to statesmanship, and in a very short period of time, the New Botany became everywhere firmly established.