Makers of British botany/John Stevens Henslow 1796—1861

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Makers of British botany
John Stevens Henslow 1796—1861
George Henslow

Plate XIII


JS Henslow.jpg




An all-round man—appointed Professor of Mineralogy at Cambridge in 1826, but succeeds Martyn in the Chair of Botany a year later—essentially an ecologist—his famous teaching methods—"practical work"—his wide interests—country life—the educational museum—village amenities.

The scientific career and parochial life of the late Rev. Prof. J. S. Henslow, are described by my late uncle, the Rev. Leonard Jenyns, in his Memoir[1]. I propose adding and illustrating some of his more personal traits, habits and pursuits as a scientific man, and to deal especially with his educational methods. His studies in science were by no means confined to one branch, thus Geology was first ardently pursued in conjunction with Sedgwick. It was in a tour together in the Isle of Wight in 1819, that they proposed establishing a "Corresponding Society, for the purpose of introducing subjects of natural history to the Cambridge students." The outcome of this idea, which was subsequently abandoned, was the "Cambridge Philosophical Society," of which " Henslow, B.A. was elected secretary in 1821[2]."

Conchology and Entomology claimed his attention; one of his first discoveries was the rare insect Macroplea equiseti, his identical "find" being figured in Curtis' British Entomology, while he found the bivalve Cyclas Henslowiana, so named by Dr Leach, at Baitsbite on the Cam. His first and best collection of insects was presented to the Cambridge Philosophical Society. Other discoveries were made in after years, and are referred to by Jenyns.

On the death of Dr E. D. Clarke, he offered himself for the Professorship of Mineralogy. Chemistry, as well as the study of Minerals, now occupied his attention. He was only 26 years of age, and still B.A., when elected to that chair. At the age of 27 he published his Syllabus of Mineralogy in 1823, "A useful manual of reference to all persons studying Mineralogy, independently of the immediate circumstances which led to its publication[3]."

In 1827 Prof. Martyn died and Prof. Henslow was elected to the chair of Botany, being succeeded by Whewell on resigning the Professorship of Mineralogy. He now turned his attention to the study of Botany; but he never paid much heed to systematic botany, for his taste lay in the direction of what is now called Ecology. He then wrote "Botanists would rather receive one of our most common weeds from a newly-discovered or newly-explored country, than a new species of an already known genus. There are higher departments of Botany than mere collectors of specimens are aware of; for to ascertain the geographical distribution of a well-known species is a point of vastly superior interest to the mere acquisition of a rare specimen." À propos of this he made elaborate epitomes of the Botanical Geographies of De Candolle, and of the writings of Humboldt, Poiret and others. His MS. is not unlike a forerunner of Schimper's Botanical Geography of to-day. He thus expressed himself in the Introduction to his Descriptive and Physiological Botany (1836): in the second section headed Botany..."This enquiry should extend as well to the investigation of the outward forms [of plant organs] and the conditions in which plants, whether recent or fossil, are met with, as to the examination of the various functions which they perform whilst in the living state and to the laws by which their distribution on the earth's surface is regulated." Again, in the Preface to the Flora of Suffolk by himself and E. S. Skepper, he wrote:—"We had thought of saying something in regard to the Geographic distribution of the species, but found our material insufficient for treating this question to advantage." As an alternative he suggests interleaving the 'Catalogue,' as the book was also called, in which observers could add observations on the Geological formations and superficial soils upon which each species grows, e.g. Chalk, the Crags, Gravels of post-tertiary period, &c. as well as maritime, marshy, boggy, healthy and cultivated soils[4]."

Though he wrote against mere collecting, he was an insatiable collector himself; but it was always with some definite, useful and generally educational purpose, and the best of his collections invariably went to museums, especially those of the Philosophical Society of Cambridge, of Kew and of Ipswich. The first still has the fishes he collected at Weymouth in 1832, solely for his brother-in-law L. Jenyns, the author of The British Vertebrate Animals.

One of the first things to which his attention was directed was the Cambridge Botanic Garden. It was far too small and in the centre of the town, where the scientific buildings are now erected. He urged the necessity of a new one, but it was not till 1831 that the present site was secured; the first tree, however, was not planted until 1846.

His educational method of teaching was totally different from the mere instructional method of all previous lecturers. To cram up facts was the students' duty in the Medical schools, where botany was supposed to be taught. To learn by their own discovery was his new method, and so each student educated himself by examining and recording plant structures first seen by his own dissections. Having long been in the habit of observing himself, he was early convinced of the importance of practical work and he always had "demonstrations," as he called them, from living specimens. Each member of the class had a round wooden plate for dissecting upon. He had only sixteen lectures to give, but he succeeded in arousing an enthusiasm in some, and interest in all who attended, and thus many came besides undergraduates, as Dr Ainslie, the Master of Pembroke.

The value of "practical work" put a stop to cram, and he was the first to introduce the examination of flowers, not only at Cambridge but for the degrees in the University of London. "He insisted," wrote Dr Hooker, "that a knowledge of physiological botany, technical terms, minute anatomy, &c. were not subjects by which a candidate's real knowledge could be tested, for the longest memory must win the day, the less did it test the observing or reasoning faculties of the men. He, therefore, insisted in all his examinations that the men should dissect specimens, describe their organs systematically and be prepared to explain their relations, uses and significations in a physiological and classificatory point of view; and thus prove that they had used their eyes, hands and heads, as well as their books[5]."

His natural bent and interest were in the investigations of the phenomena of plant-life, e.g. the colours of flowers, the laws of phyllotaxis and what would now be called biometrical studies, e.g. of the variations in the leaves of Paris and the cotyledons of the sycamore, hybridization, teratology and the origin of varieties, etc. The geographical distribution of plants and the effects of external agencies upon them were also specially studied, as is recorded in the note-book mentioned. He was thus a genuine Ecologist without knowing it. He published about 50 papers on botanical subjects during his professorship from 1825 to 1861, in which he was more than once the pioneer of special branches of study since taken up, as in the above mentioned hybridization and varietal differences under cultivation, etc.; for experiments were made on the specific identity between the Primrose, Oxlip, Cowslip and Polyanthus. He raised many varieties, which were often permanent or "Mutations"; though sometimes reversions appeared, concluding that when one form thus changed to another that was sufficient proof of identity.

Though his occupations were necessarily much changed at Hitcham, of which he became the Rector in 1838, from those at Cambridge, he by no means neglected science; but he utilized it in different ways. Thus having a good knowledge of chemistry, he endeavoured to make the farmers interested in more scientific methods of farming than they had been accustomed to. He gave lectures on the fermentation of manures and he wrote fifteen "Letters to Farmers," first published in the Bury Post and then separately. He even proposed that they should make experiments themselves. For this purpose he issued schedules to about 70 farmers who asked for them.

The experiment was to test Liebig's suggestion that gypsum should be added to manure heaps to fix the ammonia. Unfortunately there is no record of the results[6].

The most important discovery from an industrial point of view, due to his knowledge of Geology, was undoubtedly that of the phosphate nodules known in the trade as "Coprolite," at Felixstowe in 1843, when he and his family were staying there. The cliffs are formed of "London clay," topped by the "Red Crag," between which is a bed of rolled, brown pebbles, once, with the crag, forming an ancient beach. Where the white "Coralline[7]" Crag occurs, the pebble bed lies below it. This accounts for the fact that it contains remains of Miocene animals, such as teeth of the Hipparion, or ancestor of the horse.

As the sea is always encroaching, the cliff has much "talus" in places, upon which was strewed the debris from the crag, including vast quantities of pebbles. Observing that they often contained a shark's tooth or other organic remains, he suspected that they might be composed partly of phosphate of lime. This proved to be the case, for the first analysis made by Mr Potter of Lambeth showed 54% (1844). He communicated the fact to Mr, subsequently Sir, John Bennet Lawes, who desired a ton of nodules to be forwarded to him for experiment. This led to their becoming a recognised article of trade. Large fortunes have been realised in Suffolk by owners of land containing the nodule bed, though frequently occurring at a considerable depth.

In 1848 he advocated the use of phosphate nodules in the "Greensand" beds of Cambridgeshire. These also soon became a commercial commodity.

In 1849, Professor Henslow delivered the inaugural address on the foundation of the Ipswich Museum, the object being, for "Giving Instruction to the working Classes in Ipswich in various branches of Science and more especially Natural History." It affords the best example of his views generally upon the uses of Science, not only as being of indisputable value in all useful arts, but as a means of education by dispelling the then prevailing ignorance and harmful prejudices rife in those days, even among men learned in other subjects at our Universities.

He illustrates his remarks from the chief sciences, as in Astronomy, by its importance in understanding the laws of storms and tides, which Whewell was then studying. Agriculture was touched upon, in showing the importance of a knowledge of Vegetable Physiology, and illustrated by the parasites, yellow Rattle and Wheat-rust. He insisted upon the educational value of accuracy, demanded of the scientist, and the avoiding a priori assumptions and hastily drawn deductions from insufficient data. But even the philosopher himself does not always escape from the imputation; for the farmers at Hitcham were firmly convinced that the "Piperage" or Barberry itself blighted the wheat. The Professor could not convince them that the red colour of the spots on the leaves of the bush was not due to the same fungus as that on the wheat. Indeed, he observes (in a MS.): "It is not likely (as some suppose) that it is due to the influence of Æcidium berberidis." We now know that the farmers were nearer the truth and the botanists were wrong. But one point the Professor established—and I possess his dried specimens to this day—and that was, that the "mildew," a black fungus, subsequently arises from the same substratum or mycelium as the rust. The mildew, then, throws off orange-coloured dust-like "spores," which attack the Barberry, and so the cycle is completed[8].

I still possess his dried specimens of other species of Æcidium attacking various kinds of plants, which he collected for comparison with that of the Barberry.

As abortive attempts to find coal had been made in some counties, he pointed out the value of Geology in at least intimating where coal was possible and also where it was impossible. It was not, he said, that a "little knowledge is a dangerous thing," as no one would become learned if he did not begin with a little, but it was the hasty deductions that were valueless and often dangerous.

As a practical illustration of this under the false assumption that the roots made the "bulb" of mangold-wurzel, he noticed the common practice of stripping off the leaves of plants, and explained to them that unless they were required for fodder, it was a wasteful practice, as the leaves (and not the roots, as they supposed) were the makers of the "bulbs." Indeed, in 1860, Prof. Jas. Buckman proved that it lessens the weight of mangold-wurzel by nearly one half.

Science was not even shut out at the Hitcham Horticultural Society's Exhibitions, for he always had his own marquee erected and a large board over the entrance with "The Marquee Museum" upon it, the letters being composed of Hitcham freshwater mussel shells. During the day of the show, he would deliver "lecturets" from time to time on the various specimens exhibited.

The following are samples of the latter. Cases of land and fresh-water shells of Hitcham. Photographs of microscopic objects enlarged, including the first ever made, by the Rev. H. Kingsley, Tutor of Sidney College, Camb. in 1855. A case containing living specimens of the smallest British Mammal, the harvest mouse. Pearls from British molluscs. The slow-worm and viper in spirits, to show their differences. Hornets' and wasps' nests, naturally mounted, taken by himself, etc.

The Monday afternoon lessons in botany in the village school-room, held after school-hours, were always remarkable for the enthusiasm exhibited by the children. They were perfectly voluntary, but none was admitted to the Third Class until the child had learnt to spell correctly thirteen terms of classification of the classes, divisions and sections. On entering the class they at once began to fill up the "Floral Schedule[9]."

The botanical lesson included:—

1st—Inspection of specimens, anything special noticed and explained.

2nd—"Hard word" exercises. Two or three words (botanical terms) given to be correctly spelt on the next Monday.

3rd—Specimens examined and dissected and floral schedules, traced on slates, to be filled up. Marks allowed for accuracy, etc.

4th—Questions on the plant "organs."

Botanical excursions were made for those only who had received a sufficient number of marks.

The First Class came at certain times to the rectory on Sunday afternoons after Divine Service; when objects of natural history were shown and "such accounts given of them as may tend to improve our means of better appreciating the wisdom, power, and goodness of the Creator[10]."

A printed list of all the wild flowers in Hitcham was always suspended in the school-room, and a rack for named phials, which the children had to keep supplied with flowers as they came into blossom. Of course, little rewards were given to those who first found a flower and those who supplied the greater number, etc.

One of the exhibits of the Horticultural Shows was the collections of wild flowers made by the children. In addition, a public examination in botany was held, and a stranger would often find it a difficult matter to puzzle one of the best pupils, not merely as to the name—a trivial matter—but as to the structure of the flower itself.

The Government Inspector in 1858, wrote as follows in his Report:—"Extra subjects, pretty fair, and among them Botany, excellent; this last being most thoroughly yet simply taught, and by such a system that there can be no cram. As far as a child goes, it must know what it does. The good moral effect of this study on the minds of the children is very apparent."

In those days, I am speaking of the "fifties," Darwin had not enlightened us as to the wonderful adaptations of flowers for fertilization by insects. This adds enormously to the interest of the study—as the present writer soon found with village children of the parishes in which he has lived, and taught them botany—but even without that attraction the Hitcham children were intensely enthusiastic.

The Professor also taught them how to dry plants. The village Herbarium, containing all the plants growing wild in Hitcham, was entirely made by them.

It may be asked by cynics, "What can be the use of teaching science to such children?" It is not the mere fact that a child knows the structure of a rose, but it is the training in accuracy of observation, mind and habit, which the minute and close observation demands, i.e. if it be properly taught, and to secure that, is all important in children, who are naturally inattentive and inaccurate in consequence. In teaching them botany as described above, the child is trained to avoid this bad habit in an interesting way, because inattention is solely due to want of interest.

The Ipswich Museum was a great source of pleasure to him. As President he carried out his plan of making it a "typical" museum, never letting it degenerate into a mere show, as so many country museums are, or at least used to be. The Ipswich Museum has been a model for all others in that typical series of fossils, etc., are exhibited in the visible cases, all others being relegated to drawers, for students to examine.

In allusion to the uses of Museums in his inaugural address referred to above, he remarked:—"Our collections should be viewed as the means of assisting us in the acquisition of real knowledge, and not merely to be gazed at as raree shows, or as only valuable in proportion to the number or scarcity of the objects they contain."

Of course, periodical lectures were delivered by the Professor at Ipswich, and he was a most lucid and admirable exponent.

He was the first to maintain that in museums of animals, they should, whenever possible, as, e.g. with birds, be represented in their natural conditions. With this object he collected nests with the boughs, or whatever it was in which they rested. Since then this plan has been admirably carried out at the Natural History Museum, South Kensington. He also supplied several museums with wasps' and hornets' nests with their surroundings. The plan he discovered most convenient for taking them, was to saturate tow with spirits of turpentine and place it at night in the hole, covered over with an inverted and corked flower-pot. The nest could then be dug up with impunity, as all the wasps were dead or torpid by the following morning. He always preserved the "pavement" or bottom-soil covered with stones which accumulated as the hollow for the nest increased in size. The nest was then suspended over it on rods to show the exact position. It was also half-dissected, to exhibit the interior, all the grubs having been carefully extracted. The village carpenter, the late Mr W. Baker, was a most enthusiastic assistant in taking and mounting the specimens.

When the potato famine occurred in Ireland in 1845—46, the disease was very prevalent in Hitcham. This induced the Professor to explain to his parishioners and others—for he published his recommendations—how they could utilise their rotten potatoes by extracting the valuable starch, which still remained sound within the tubers, even when these were refused by pigs. The process is so simple that it may be mentioned here. The potatoes must be grated (a piece of tin with holes punched through it will do); the pulp is then stirred with a stream of cold water through a hair-sieve. The brown water must be allowed a few minutes for the starch, carried through, to settle. The water is poured off, and the layer of starch must be stirred up and washed with fresh cold water. This may be done two or three times, till it becomes perfectly white. It must then be carefully dried in the sun or in a warm room (our method was to hang it up in small muslin bags in the kitchen); the bags must be repeatedly "kneaded" to prevent its clotting. When perfectly dry, it will keep for any length of time. Of course, it is precisely the same thing as sago, tapioca, cornflour, arrowroot, etc. and can be used like them. All our potatoes in the Rectory garden were rotten, but we recovered at least two sacks of starch. I remember taking a large sponge-cake to school, more or less made with this potato-flour, and making my reverend master somewhat incredulous by telling him it was made out of rotten potatoes!

Professor Henslow printed and circulated the receipt for the extraction of starch, in the village; so that several, who thought it worth while, obtained considerable quantities of starch.

In one of his lectures, dealing with this subject, he pointed out how a good basin of "arrowroot" can be made in ten minutes from two or three fair-sized potatoes; for as soon as the starch has been thoroughly "washed," it is ready for the boiling milk. It is essential the milk or water should be actually boiling, or the granules of starch do not burst and so make the required "jelly."

The school children of Hitcham were by no means left out in the cold as to the knowledge of natural phenomena. They were early instructed as to the harmless nature of toads and slow-worms, which were very abundant, on the one hand; and of the danger of handling a viper, on the other. This last is the only poisonous reptile in England, and easily recognisable by the lozenge-shaped marks down the back. Having specimens in spirit, they had no excuse for confounding them; but, as always happens with children, if there is an alternative of any sort between which they are well taught the difference, some one is sure to get them transposed in his memory. Consequently, a boy came up to the Rectory with his arm greatly swollen; he had been bitten by a viper which he had taken up, thinking it was a slow-worm, because, as he said, it had the marks along its back!

Besides the tiny harvest mice, he at one time possessed for some two or three years two "pet" Jersey toads, or the great crapaud. They were kept in a wire-gauze cage, and it was our delight as children to feed these monsters every morning. A butterfly net swept over the lawn was sure to secure all sorts of flying and jumping creatures. The lid of the cage being lifted up, the net was turned inside out over the toads, and quickly closed. Then began the matutinal breakfast. They would never notice anything that did not move. Seeing, however, say a grasshopper, stir, the toad would stalk it like a cat after a bird; and when within tongue-shot, out came its long tongue like a flash of lightning, and the grasshopper vanished in the flash. Worms were a great delight. Snapping up one in the middle, the two ends were carefully cleaned from earth by passing them between the toes two or three times; then followed a mighty gulp, and all was over.

Shell-traps were always laid about the grass, consisting of slates, under which there would generally be found a various crop of sorts. I have now two glass cases containing all the shells, land and fresh-water, of Hitcham, mounted by the Professor himself. A reward was offered for every specimen of a Helix with the shell reversed. They are very rare, but one was brought by a little boy who discovered it, for he found he was unable to get his thumb into the opening the right way when playing at "conquerors." So he got the only sixpence earned in twenty-three years that the Professor was incumbent of Hitcham. The collection of butterflies was always being added to; now and then a rare one would appear at Hitcham, as, e.g. the Camberwell Beauty. The Professor was walking in the Rectory garden with the late Judge Eagle, of Bury St Edmunds, when one settled on a wall. Mr Eagle stood sentry while the Professor ran indoors for his net. It need hardly be added that the specimen still rests in the collection, which passed into the possession of his son-in-law, the late Sir J. D. Hooker, F.R.S., etc.

I cannot do better than conclude with my uncle's words at the end of his Memoir:—"When a good man dies the world does not cease to benefit from those labours of love which he undertook for his fellow men. Though personally removed from them his example remains; his voice too, is still heard in the lessons left to be handed down to those who come after him. The influences of Professor Henslow's teaching have been felt in other places than those in which he himself taught, they have borne fruit far beyond the obscure neighbourhood in which he first sowed the good seed, and who shall say to what further results they may not grow in years to come, bringing honour to his memory, and what is far more, glory to God? 'A word spoken in due season, how good is it!'"


  1. Memoir of the Rev. John Stevens Henslow, M.A., F.L.S., F.G.S., F.C.P.S. (J. Van Voorst, 1862).
  2. Memoir, pp. 17 ff.
  3. Memoir,p. 29.
  4. Such are the "Conditions of Life," upon the "Direct Action," of which Darwin lays so much stress, as resulting in "Definite Variations...without the aid of selection." (Var. of An. and Pl. under Dom. II. p. 271 ff.; Origin etc. 6th ed. p. 106, etc.)
  5. Quoted in Memoir, p. 161.
  6. On enquiring at Rothamstead, Mr Hall has kindly informed me that a "good deal of attention was given in Germany to this and other possible materials for the conservation of the nitrogen; but the general result was adverse to their employment."
  7. A misnomer, as the coralloid organisms are Bryozoa.
  8. In his printed Report on the Diseases of Wheat, written for private circulation only, he has added in MS.—"In specimens of true mildew, the three formsUredo rubigo, U. linearis and Puccinia graminis, coexist simultaneously in the same sori, as well as numerous intermediate forms, which establish the specific identity of these fungi." U. rubigo-vera is now regarded as a form of Puccinia rubigo-vera and Æcidium asperifolii.
  9. From the Professor's display of the methods he adopted of teaching Botany in schools, now in the South Kensington Museum, and Prof. D. Oliver's Lessons, etc. based on MS. left unfinished at my father's death, the floral schedule has been adopted in schools, not only all through the British Isles, but the Colonies as well.
  10. A completer account will be found in Jenyns' Memoir.