Part 33

It is idle to speculate on what might have happened had such a wide observer as Griffith chanced on the clue. In this respect he was of his time as most are. The man who put the industrious but blind gropings of this period in morphological botany straight, both as regards the development of the embryo and the comparative ontogeny of archegoniate plants was Hofmeister, and like all exceptional men he belonged to the new period created by him.

The great advantage of this course of lectures seems to me to be that it approaches the study of the history of botany in the right way; for progress in our science has been the result of individuals rather than of schools. The consideration of the work of Griffith from 1832 to 1845 is a vivid illustration of the condition of morphological botany in the earlier portion of the period, surveyed in one of the chapters in Sach's History under the title of "Morphology and Systematic Botany under the influence of the History of Development and the knowledge of the Cryptogams." These two subjects were always before Griffith.

The interest of the personality of William Griffith and of the work he accomplished in his tragically short life is obvious. Not less so is the way in which that work was done inside the limitations of his period. We, who are still gleaners in the field that Griffith and his contemporaries cleared and Hofmeister marked out and tilled, are probably just as incapable of conceiving the future developments of morphology.

ARTHUR HENFREY

1819-1859

BY F. W. OLIVER

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.