Makers of British botany/Nehemiah Grew 1641—1712
Ancestry and Life narrative—his versatility—state of Botany—Grew and Malpighi—Grew's bona fides vindicated—The Anatomy of Vegetables Begun—seed structure—his treatise on the Root—its dedication—The Anatomy of Trunks—The Anatomy of Plants—illustrations—Grew's conception of cells and tissues—the plant as a textile fabric—analogy with the animal body—medullary rays—secondary thickening—his understanding of external morphology—physiological notions—suggestions for experiments—importance of the habitat—the sexes of flowers—floral and seed structure—estimate of his contributions to Botany.
Nehemiah Grew, who, with the Italian botanist Marcello Malpighi, may be considered as co-founder of the science of Plant Anatomy, lived in stirring and troubled times. His life extended from 1641 to 1712; that is to say, he was born the year before King Charles I proclaimed war upon the parliamentary forces, and he lived through the Protectorate, the reigns of Charles II, James II, William and Mary, and the greater part of the reign of Queen Anne. He came of a stock remarkable for courage and independence of mind. His grandfather, Francis Grew, is described as having been a layman, originally of good estate, but "crush'd" by prosecutions for non-conformity in the High Commission Court and Star Chamber. Francis Grew had a son Obadiah, who was a student of Balliol, and entered the Church. When the Civil War broke out, he sided with the parliamentary party, but was by no means a blind adherent of Cromwell, with whom he is said to have pleaded earnestly for the life of King Charles I. In 1662 Obadiah Grew resigned
NEHEMIAH GREW (1701)
Portrait of Nehemiah Grew after the portrait by R. White which is
his living, being unable to comply with the Act of Uniformity. Twenty years later, as a man of seventy-five, he was convicted of a breach of the Five Mile Act, and imprisoned for six months in Coventry Gaol. But though by this time his sight had failed, his spirit was indomitable. Whilst in prison, he dictated a sermon every week to an amanuensis, who read it to several shorthand writers, each of whom undertook a number of copies; it was then distributed to various secret religious meetings, at which it was read. Nehemiah Grew was Obadiah's only son, and it is a curious fact that the year 1682, which witnessed the father's imprisonment, was the year in which the son published his magnum opus, The Anatomy of Plants, prefaced by an Epistle Dedicatory to "His most sacred Majesty Charles II." So far as one can gather, Nehemiah Grew's career seems to have been singularly unaffected by the political crises that took place around him. The deliberate style of his writing certainly suggests a studious and unruffled life. He was an undergraduate at Pembroke Hall, Cambridge, and afterwards took his doctor's degree in medicine at Leyden, at the age of thirty. He seems to have been successful in his profession, and we learn from the sermon preached at his funeral that he died suddenly, whilst still actively engaged in his practice. In the words of the sermon, "It was his Honour and Happiness, to be Serviceable to the last Moments of Life."
Before turning to Grew's botanical work, it may be worth while to refer very briefly to his writings on other subjects, showing as they do the remarkable versatility of his mind. He produced a series of chemical papers, and also pamphlets on the method of making sea-water fresh, and on the nature of the salts present in the Epsom wells. In 1681 appeared his Musæum Regalis Societatis, a catalogue raisonné of the objects in the Museum of the Royal Society, with which were bound up some contributions to animal anatomy. The Catalogue is a bulky volume, and it is hard to forbear a smile on reading that Grew dedicated it to one Colwall, the founder of the Museum, in order that the Royal Society "might always wear this Catalogue, as the Miniature of [his] abundant Respects, near their Hearts." As we should expect, this Catalogue is far more discursive than such a work would be if it were drawn up at the present day, though Grew takes credit to himself for not "medling with Mystick, Mythologick, or Hieroglyphick matters." He manages, however, to introduce some general remarks which are of interest. He realises, for instance, that it is possible to group living creatures in a way which has some significance, and that it is the business of the biologist to discover this grouping. He blames Aldrovandus for beginning his history of quadrupeds with the horse, because it is the most useful animal to man, and points out that Gesner's arrangement, which is purely alphabetical, is even less satisfactory. "The very Scale of the Creatures," he concludes, "is a matter of high speculation." It is tempting to quote largely from the Catalogue, but I will confine myself to one other remark of Grew's which is perhaps particularly applicable to-day, when the quotation of authorities is apt to become almost an obsession: "I have made the Quotations," he says, "not to prove things well known, to be true;…as if Aristotle must be brought to prove a Man hath ten Toes."
Grew's last work was the Cosmologia Sacra, a folio volume occupied with a defence of Christianity, and an explanation of the author's views on the nature of the Universe. There is a copy in the British Museum, the earlier part of which is crowded with marginal and fly-leaf notes, in some cases initialled or even signed in full by Samuel Taylor Coleridge. One cannot help recalling Charles Lamb's humorous complaint that books lent to Coleridge were apt to be returned "with usury; enriched with annotations tripling their value…in matter oftentimes, and almost in quantity not unfrequently, vying with the originals." Coleridge seems to have accepted Grew quite seriously as a thinker. In one of his manuscript notes we read, "It is from admiration of Dr N. Grew, and my high estimate of his Powers, that I am almost tempted to say, that the Reasonings in Chapt. III ought to have led him to the perception of the essential phænomenality of Matter." That these reasonings did not so lead him, must, I think, be attributed to the fact that Grew was above all things a naturalist, and Coleridge a philosopher, and that between the two an intellectual gulf is often fixed.
After this somewhat lengthy introduction, it is more than time to turn to our main subject,—the study of Nehemiah Grew's work as a botanist.
Botanical science was in a decidedly decadent condition when Grew entered the field. The era of the herbal was closing. The last English book of any importance which can strictly be included under this head, Parkinson's Theatrum Botanicum, was published the year before Grew was born, and a lull in this kind of work followed. It is true that Culpeper's Herbal appeared later, but this bombastic work was of no botanical value. It was reserved for Morison and Ray to open a new era in British Systematic Botany. At the same time, fresh inspiration was being breathed into the science from quite a different quarter. The herbalists studied plants primarily with a view to understanding their medicinal properties. Nehemiah Grew also approached Botany in the first instance from the medical standpoint, but it was his knowledge of anatomy which opened his mind to the possibility of similar work, with the bodies of plants, instead of those of animals, as the subject. He tells us that he was impressed by the fact that the study of animal anatomy had been carried on actively from early ages, whereas that of vegetable anatomy had been scarcely so much as contemplated. "But considering," he continues, "that both came at first out of the same Hand, and are therefore the Contrivances of the same Wisdom; I thence fully assured my self, that it could not be a vain Design, though possibly unsuccessful, to seek it in both."
Grew was drawn to the study of plant structure at the age of twenty-three, and seven years later he produced his earliest work on the subject, The Anatomy of Vegetables Begun, which was published by the Royal Society in 1672. It will be remembered that the Royal Society was then quite in its youth, its first beginnings only dating back to about 1645. By a curious coincidence,—recalling the classic case of Darwin and Wallace at the Linnean Society,—on the very day that Grew presented his treatise in print, the Secretary of the Royal Society received Marcello Malpighi's manuscript dealing with the same subject. Priority can however be fairly claimed for the Englishman, since he had submitted his treatise to the Society in manuscript earlier in the year. This question of priority, and also the question whether Grew was guilty of plagiarism from Malpighi's writings, has been much discussed at different times. Schleiden in particular brought forward charges of the most serious nature against Nehemiah Grew's good faith. These accusations were, however, dealt with in detail in a pamphlet by Pollender in 1868, and shown to be groundless, Schleiden's information about the circumstances being wholly inaccurate. There is now practically no doubt that Grew was an independent worker, and was only definitely indebted to Malpighi, in so far as he himself acknowledges it. In the preface to the second treatise, for instance, he mentions the Italian botanist, and remarks in speaking of the "Air-vessels"—"the manner of their Spiral Conformation (not observable but by a Microscope) I first learned from Him, who hath given a very elegant Description of them." If Grew had been a wholesale plunderer from Malpighi's writings, he would scarcely have been likely to have acknowledged indebtedness on a special point. It must be confessed, however, that judging by present-day standards of scientific etiquette, Grew should have referred more fully to the works of the Italian author, in his final book, The Anatomy of Plants.
The Anatomy of Vegetables Begun contains more that is of interest from a morphological than from a strictly anatomical
Plate from Anatomy of Vegetables Begun, 1672
Figs. 1–4, Bean Seed; 1, Bean opened out; 2, Same to
standpoint, according to the modern sense of the terms. In botanical language, the meaning of the word anatomy has become restricted since Grew's time, until it is now often used to denote microscopic detail alone. Grew devotes a good deal of space to the study of seed structure, dealing chiefly with such features as can be observed with the naked eye (Pl. 5). He invented the term "radicle" for the embryonic root, and used the word "plume" for the organ which we now speak of in the diminutive as the plumule. The cotyledons he called "lobes," but he recognised that they might in some cases appear above ground and turn green, becoming in his terminology "dissimilar leaves." He took the Bean seed as his principal type, and described it with the lucid picturesqueness which is so characteristic of his writing. It is, he says, "cloathed with a double Vest or Coat: These Coats, while the Bean is yet green are separable and easily distinguished. When 'tis dry, they cleave so closely together, that the Eye, not before instructed, will judge them but one; the inner Coat likewise (which is of the most rare contexture) so far shrinking up, as to seem only the roughness of the outer, somewhat resembling Wafers under Maquaroons. At the thicker end of the Bean, in the outer Coat, a very small Foramen presents it self:… That this Foramen is truly permeable even in old setting Beans, appears upon their being soak'd for some time in Water: For then taking them out, and crushing them a little, many small Bubbles will alternately rise and break upon it."…The Plume "is not, like the Radicle, an entire Body, but divided at its loose end into divers pieces, all very close set together, as Feathers in a Bunch; for which reason it may be called the Plume. They are so close, that only two or three of the outmost are at first seen: but upon a nice and curious separation of these, the more interiour still may be discovered…. In a French Bean the two outmost are very fair and elegant. In the great Garden-Bean, two extraordinary small Plumes, often, if not always, stand one on either side the great one now describ'd." These two "extraordinary small plumes" are, in other words, the structures which we should now describe as buds in the axils of the cotyledons. Grew also notices that two simplified leaves are borne next above the cotyledons, or, as he expresses it, the "Plume" is "cooped up betwixt a pair of Surfoyls."
Grew deals also with the vernation of leaves, and methods of bud protection. He shews that their position and folding gives "two general advantages to the Leaves, Elegance and Security, sc. in taking up, so far as their Forms will bear, the least room; and in being so conveniently couch'd, as to be capable of receiving protection from other parts, or of giving it to one another; as for instance, First, There is the Plain-Lap, where the Leaves are all laid somewhat convexly one over another, but not plaited; being to the length, breadth and number of Leaves most agreeable; as in the Buds of Pear-tree, Plum-tree, etc. But where the Leaves are not thick set, as to stand in the Plain-lap, there we have the Plicature; as in Rose-tree, Strawberry, Cinquefoyl, Burnet etc." Grew refers also to rolled vernation, distinguishing between the "Fore-Rowl" and the "Back-Rowl." He thus remarks on the hairy covering characteristic of young leaves:—"the Hairs being then in form of a Down, alwayes very thick set, thus give that protection to the Leaves, which their exceeding tenderness then requires; so that they seem to be vested with a Coat of Frieze, or to be kept warm like young and dainty Chickens, in Wooll."
In the year following the publication of The Anatomy of Vegetables Begun, Nehemiah Grew produced a second treatise, under the title, "An Idea of a Phytological History Propounded. Together with a Continuation of the Anatomy of Vegetables; Particularly prosecuted upon Roots. And an Account of the Vegetation of Roots Grounded chiefly thereupon." In the dedications of his books Grew often reveals much of his own personality, and of his attitude towards science, although such revelations are apt to be mingled with the curious "conceits," and extravagant flattery, characteristic of the time. For instance he dedicated this particular work to the President and Fellows of the Royal Society, and after addressing to them some apologetic remarks about his own performance, he takes heart of grace from the thought that "how unpromising soever the Stock may be, yet the Fruit cannot but be somewhat matured upon which You are pleas'd to shine." It shews how strong the influence of fashion can be, when we find such bombast coming from the pen of a man who, only a few lines earlier, has written, with the perfection of simplicity, "Withal, I looked upon Nature as a Treasure so infinitely full, that as all men together cannot exhaust it; so no man, but may find out somewhat therein, if he be resolved to try."
The most important part of this treatise is the account of the comparative structure of roots, to which we will return later, when discussing Grew's anatomical conceptions. With regard to the position of the plant in the soil, he held somewhat mystical views. He believed that the "air-vessels," or tracheal elements, tended to draw the plant upwards, and the roots to pull it downwards. He says, for example, that the upper part of the roots of most seedlings ascend, because the first leaves being large and standing in the open air, "the Air-vessels in them have a dominion over the young Root, and so yielding theselves to the sollicitation of the Air upwards, draw the Root in part after them."
In 1675 appeared Grew's third botanical work, The Comparative Anatomy of Trunks, which dealt with stem structure, as the previous work dealt with root structure. There is, in the British Museum, a particularly interesting copy of this book, which is elaborately annotated in manuscript. From internal evidence it seems almost certain that this is the author's copy, corrected in his own handwriting. Some, though not by any means all, of the corrections are identical with the alterations found in the 1682 edition. Above the first plate is written "vide ye Book Interleavd," and we may perhaps hazard the guess that in this copy we have Grew's first suggestions, whilst those which he finally adopted in the second edition were inserted in the interleaved copy whose whereabouts, if it still exists, is unknown at the present time.
Pl. 6 shews a typical page from the annotated copy. At the foot we find the note "Air-Vessels out of Parenchyma, transformed, as Caterpillars to Flys," shewing that Grew had arrived at some idea of the formation of vessels. The whole section of the book to which this page belongs is very much remodelled in the 1682 edition, but the analogy just quoted is introduced and Grew proceeds accurately to describe the origin of vessels. "And as the Pith it self, by the Rupture and Shrinking up of several Rows of Bladders, doth oftentimes become Tubulary: So is it also probable, that in the other Parenchymous Parts, one single Row or File of Bladders evenly and perpendicularly piled; may sometimes, by the shrinking up of their Horizontal Fibres, all regularly breakone [sic] into another and so make one continued Cavity."
I have passed over these three treatises in a somewhat cursory fashion, because Nehemiah Grew's botanical work is perhaps better studied in his final pronouncement on the subject, a folio volume published in 1682 under the title of "The Anatomy of Plants. With an Idea of a Philosophical History of Plants. And several other Lectures, Read before the Royal Society." This work consists of second editions of his three earlier treatises, largely rewritten, with a great deal of additional matter, including a section on the anatomy of flowers, and many new figures. Some of the plates are excellent, and especially remarkable for the way in which Grew shews the anatomy in drawings which represent the organ in three dimensions (Pl. 7). He himself laid great stress on this. In his own words, "In the Plates, for the clearer conception of the Part described, I have represented it, generally, as entire, as its being magnified to some good degree, would bear….So, for instance, not the Barque, Wood, or Pith of a Root or Tree, by it self; but at least, some portion of all three together: Whereby, both their Texture, and also their Relation one to another, and the Fabrick of the whole, may be observed at one View." One cannot help wishing that botanists of the present day would more often take the trouble to illustrate their papers on this principle.
It is as a plant anatomist that Grew is chiefly famous, and it is important to try to realise exactly how far his conception of the anatomical structure of plants has been confirmed by
more recent research. In appraising his work it must be remembered that he was essentially the pioneer of the science. It is true that some observations on plant anatomy occur in Robert Hooke's Micrographia, which was published six years before Grew sent in his first manuscript to the Royal Society; but Hooke never really attempted to make a systematic study of the subject. He had succeeded in greatly improving the microscope, and his chief interest was in applying his instrument to all kinds of bodies, vegetable and otherwise. Cork, charcoal, pith, etc., came under his observation, and to some extent he understood their structure. Grew acknowledges indebtedness to "the Learned and most Ingenious Naturalist Mr Hook" and tells us that some of the results which Hooke obtained, inspired him to study certain of his plants again with a better microscope. For instance Hooke was able to see smaller pores in wood than Grew had been able to detect, but, with better glasses, he confirmed the accuracy of Hooke's observation. However, although Hooke must certainly be credited with priority in the discovery of the fact that plant tissues are characterised by a cellular structure, his botanical work, considered in its entirety, is of very slight significance compared with that of Grew.
Grew's clearest account of plant cells is perhaps to be found in his description of root parenchyma, which he compares to "the Froth of Beer or Eggs" or to "a fine piece of Manchet," or again, to "a most curious and exquisitely fine-wrought Sponge." He quotes with approval Hooke's description of Elder-Pith as "an heap of Bubbles" It would be unsafe however to conclude that he had really arrived at what is known as the Cell Theory. His conception of the nature of plant tissues was not by any means that of the modern botanist. He believed the cell-walls to consist of interwoven fibres, which were continuous from cell to cell. He did not consider that these fibres were invariably wrought together in such a fashion as to enclose bladder-like spaces, or cells; in some cases he held that the tissue was non-cellular, consisting simply of interwoven fibres. It was these hypothetical fibres, rather than the cells, which he regarded as of fundamental importance. His idea, which is somewhat confusing, is perhaps best understood from his comparison of plant structure with pillow lace. The "most unfeigned and proper resemblance we can," he writes, "at present make of the whole Body of a Plant, is, To a piece of fine Bone-Lace, when the Women are working it upon the Cushion, For the Pith, Insertions, and Parenchyma of the Barque, are all extream Fine and Perfect Lace-Work: the Fibres of the Pith running Horizontally, as do the Threds in a Piece of Lace; and bounding the several Bladders of the Pith and Barque, as the Threds do the several Holes of the Lace; and making up the Insertions without Bladders, or with very small ones, as the same Threds likewise do the close Parts of the Lace, which they call the Cloth-Work. And lastly, both the Lignous and Aer-Vessels, stand all Perpendicular, and so cross to the Horizontal Fibres of all the said Parenchymous Parts; even as in a Piece of Lace upon the Cushion, the Pins do to the Threds. The Pins being also conceived to be Tubular, and prolonged to any length; and the same Lace-Work to be wrought many Thousands of times over and over again, to any thickness or hight, according to the hight of any Plant. And this is the true Texture of a Plant."
Grew thus visualised the inner structure of the plant as a textile fabric, and the analogy between vegetable substance and woven threads seems to have been constantly present in his mind. The same idea also occurs, for instance, in the dedication of his magnum opus, where he says, "one who walks about with the meanest Stick, holds a Piece of Nature's Handicraft, which far surpasses the most elaborate Woof or Needle-Work in the World."
The notions at which Nehemiah Grew arrived on the subject of the vascular anatomy of plants were more advanced than his ideas on the ultimate nature of the tissues. There is no doubt that the comparison with animal anatomy, which was constantly in his mind, was on the whole helpful, though it led to some errors. The following paragraph, which occurs in the Cosmologia Sacra, seems to be an instance in which the analogy with the animal kingdom, helped him to take a broad view. "In the Woody Parts of Plants, which are their Bones; the Principles are so compounded, as to make them Flexible without Joynts, and also Elastick. That so their Roots may yield to Stones, and their Trunks to the Wind, or other force, with a power of Restitution. Whereas the Bones of Animals, being joynted, are made Inflexible."
In plants, as in animals, Grew looked for "vessels," and discovered by means of a simple experiment that continuous tubes, worthy of being called by this name, existed in the outer parts of the root, whereas the pith consisted of closed chambers. He cut a fresh root transversely, and then gently pressed the side of it with his finger nail. He was able to detect the vessels with the naked eye, and he observed that where they occurred, sap oozed out under pressure, but was sucked in again when the pressure was removed. The pressure also expressed a certain amount of sap from the pith, where vessels were absent, but here the sap was not sucked in again when the root was no longer squeezed, shewing that the liquid had only been forced out by the wounding of the cells. Had they been open tubes like the vessels, the release of the pressure would have caused the sap to disappear. Grew recognised that the vascular tissue of the root is centrally placed, whereas in the stem it is circumferential, and he points out that this difference is connected with the diverse mechanical needs of the two organs. It should also be noted that he discovered that concentration of the vascular system is characteristic of climbing plants, the wood, in his own words, standing "more close and round together in or near the Center, thereby making a round, and slender Trunk. To the end, it may be more tractable, to the power of the external Motor, what ever that may be: and also more secure from breaking by its winding Motion." He observed the radial arrangement of the xylem in the root, and offered an explanation of it, which is however scarcely free from obscurity. "Some of the more Æthereal and Subtile parts of the Aer, as they stream through the Root, it should seem, by a certain Magnetisme, do gradually dispose the Aer-Vessels, where there are any store of them, into Rays." Amongst other details of root anatomy, Grew discovered that all the tissues outside the central cylinder sometimes peel off when the root becomes old, or as he says, "the whole body of the Perpendicular Roots, except the woody Fibre in the Centre, becomes the second skin." Turning to stem structure, we find that he understood the difference in origin between stem buds and adventitious roots. The stem bud, he writes, "carries along with it, some portion of every Part in the Trunk or Stalk; whereof it is a Compendium." The adventitious root, on the other hand, "always shoots forth, by making a Rupture in the Barque, which it leaves behind, and proceeds only from the inner part of the Stalk." He describes the vascular bundles of the stem as "fibres" perforated by numerous "pores." It would be a mistake, however, to suppose that he had no understanding of their structure, at least as regards the xylem, for he goes on to say that "each Fibre, though it seem to the bare eye to be but one, yet is, indeed, a great number of Fibres together; and every Pore, being not meerly a space betwixt the several parts of the Wood, but the Concave of a Fiber." He noticed the medullary rays, for which he uses the expressive term "Insertions." "These Insertions," he says, "are likewise very conspicuous in Sawing of Trees length-ways into Boards, and those plain'd, and wrought into Leaves for Tables, Wainscot, Trenchers, and the like. In all which,…there are many parts which have a greater smoothness than the rest; and are so many inserted Pieces of the Cortical Body; which being by those of the Lignous, frequently intercepted, seem to be discontinuous, although in the Trunk they are really extended, in continued Plates, throughout its Breadth."
Nehemiah Grew was interested in the process of secondary thickening, but he only arrived at a dim notion of how it took place. He grasped, however, the important point that in a tree trunk the meristematic zone lies near the surface, "the young Vessels and Parenchymous Parts" being formed annually "betwixt the Wood and Barque." He describes how, "every year, the Barque of a Tree is divided into Two Parts, and distributed two contrary ways. The outer Part falleth off towards the Skin; and at length becomes the Skin it self….The inmost portion of the Barque, is annually distributed and added to the Wood;
|Sheweth the Parts of a Goosberry||Part of a Vine Branch cut transversly, and
split half way downe ye midle
the Parenchymous Part thereof making a new addition to the Insertions within the Wood; and the Lymphæducts a new addition to the Lignous pieces betwixt which the Insertions stand. So that a Ring of Lymphæducts in the Barque this year, will be a Ring of Wood the next; and so another Ring of Lymphæducts, and of Wood, successively, from year to year." Exactly what Grew meant by the term "Lymphæduct" is not always clear. In some cases he seems to refer to the phloem and cambium by this name, and in other cases to the perimedullary zone. The annual rings in Oak, Elm, Ash, etc. came under his observation, and he remarks that the difference between the Spring and Autumn wood, as we should now call it, arises from the fact that "the Aer-Vessels that stand in the inner margin of each annual Ring, are all vastly bigger, than any of those that stand in the outer part of the Ring."
Grew did not enter into the minuter details of histology, except in his description of the spiral tracheids, to which, as we have seen, his attention was first called by Malpighi's observations. He speaks of the spiral as formed of "Two or More round and true Fibres, although standing collaterally together, yet perfectly distinct. Neither are these Single Fibres themselves flat, like a Zone; but of a round forme, like a most fine Thred." He makes the curious statement that the direction of the spiral is constant, being "in the Root, by South, from West to East: but in the Trunk, contrarily, by South, from East to West."
Although it is as an anatomist that Nehemiah Grew is best known, his grasp of external morphology is perhaps even more remarkable. His work on seed structure has already been quoted. He seems to have quite readily detected the true nature of modified stems. He examined for instance the thorns of the Hawthorn, and saw that their structure was axial. In his own words, they "are constituted of all the same substantial Parts whereof the Germen or Bud it self [is], and in a like proportion: which also in their Infancy are set with the resemblances of divers minute Leaves." It should be recalled that Albertus Magnus, the great scholastic philosopher, writing in the thirteenth century, distinguished between thorns and prickles, and noticed transitions between the former and leafy branches. There is no reason to suppose, however, that our author was acquainted with the work of Albertus. Grew realised the nature of Bulbs, and points out that "the Strings only, are absolute Roots; the Bulb, actually containing those Parts, which springing up, make the Leaves or Body; and is, as it were, a Great Bud under ground."
Nehemiah Grew was interested in plant physiology, although the state of chemical and physical knowledge at the time did not allow of his advancing so far in this, as in the morphological side of the subject. His turn of mind, too, appears to have naturally led him to the study of form rather than that of function. As regards the absorption of water, his idea was simply that the roots sucked up water like a sponge, because the parenchyma was of a spongy nature. He supposed that the liquid was rendered purer by being strained through the skin, which, according to whether it was of a texture resembling brown paper, cotton, or leather, would produce a different effect upon any solution passing through it. His explanation of the ascent of the sap had really much in common with the "Kletterbewegung" theory propounded by Westermaier almost exactly two hundred years later. Grew argued that "considering to what height and plenty, the Sap sometimes ascends; it is not intelligible, how it should thus ascend, by virtue of any one Part of a Plant, alone; that is neither by virtue of the Parenchyma, nor by virtue of the Vessels, alone." He pointed out that the parenchyma might suck up a liquid for a short distance, and also the vessels, like "small Glass-Pipes immersed in Water, will give it an ascent for some Inches; yet there is a certain period, according to the bore of the Pipe, beyond which it will not rise." To account for the rise he supposes that the vessels and parenchyma work together, the turgidity of the surrounding parenchyma cells both compressing the vessels, and thus causing the liquid in them to ascend, and also actually forcing some of their own contents into them.
Grew performed a few experiments, especially in the direction of plant chemistry. This was a natural line of work for a doctor, since the extraction of various vegetable substances had long been practised in medicine. He noticed, amongst other points, that the green infusion obtained by treating a plant with olive oil would, at least in the case of certain aromatic plants, appear of a green colour in a small drop, but of a red, or deep yellow, when a quantity of it was held up against a candle. In other words, Grew seems to have observed the characteristic fluorescence of chlorophyll.
He was interested also in the subject of geotropism, and succeeded in proving that there is an innate tendency for the root to grow down and the stem to grow up; and that it is not merely a case of the root seeking the soil, and the stem the air. His directions for performing the experiment are as follows:—"Take a Box of Moulds, with a hole bored in the bottom, wide enough to admit the Stalk of a Plant, and set it upon stilts half a yard or more above ground. Then lodg in the Mould some Plant, for Example a Bean, in such sort, that the Root of the Bean standing in the Moulds may poynt upwards, the Stalk towards the ground. As the Plant grows, it will follow, that at length the Stalk will rise upward, and the Root on the contrary, arch it self downward. Which evidently shews, That it is not sufficient, that the Root hath Earth to shoot into, or that its Motion is only an Appetite of being therein lodged, which way soever that be: but that its nature is, though within the Earth already, yet to change its Position, and to move Downwards. And so likewise of the Trunk, that it rises, when a Seed sprouts, out of the Ground, not meerly because it hath an Appetite of being in the open Aer; for in this Experiment it is so already; yet now makes a new Motion upwards."
Although Grew cannot be called a great experimenter, he frequently took the easier course of throwing out suggestions for such work. "The generation of Experiments" he describes as "being like that of Discourse, where one thing introduceth an hundred more which otherwise would never have been thought of." Amongst other proposals he recommends that trial should be made of growing plants in common water, snow water, milk, oil, wine, ink, etc., or in any of these with solid bodies, such as nitre and salt, dissolved in them. He points out that the effect both on the plant and on the liquid should be noted. The solid body should be weighed before solution, and then, after the experiment is over, the liquid should be evaporated and the solid again weighed.
Another instance in which he suggested an experiment, apparently without carrying it out, was in relation to the movements of the stems of non-climbing plants. He seems to have anticipated the nineteenth century discovery of nutation amongst plants other than climbers, though he stopped short of actually proving it. In his account of the Motions of Trunks he remarks, "The Convolution of Plants, hath been observed only in those that Climb. But it seems probable, that many others do also wind;…Whether it be so, or not the Experiment may easily be made by tying a Thred upon any of the Branches; setting down the respect it then hath to any Quarter in the Heavens: for, if it shall appear in two or three Months, to have changed its Situation towards some other Quarter; it is certain proof hereof." He noticed that some plants twine "by South from East to West" and others "from West to East," and attributed this to their being respectively under the influence of the sun and the moon.
Whenever Grew's notions of plant physiology depended upon chemistry, they became, according to our modern ideas, extremely difficult to follow. He held, among many other curious beliefs, that salts obtained from any plant have a tendency to crystallise out in a form resembling that plant, and adds, as an illustration from the animal world, "though I have not seen it my self, yet I have been told by one that doth not use to phancy things, that the Volatile Salt of Vipers, will figure it self into the semblance of little Vipers."
The mystical belief that characteristic "principles" permeate all things, finds expression in his idea that the "frost flowers," sometimes to be seen on a window pane, are evidence that the air is impregnated with "Vegetable Principles." Another fact, which he brings forward in support of the same view, is that the ground or water, when exposed for some time to air, turns green. His explanation, in this latter case, was not far from the truth, for, as we now know, the greenness is due to the vegetation of minute algæ, which, in their dormant state, may be carried from place to place by the wind.
It is usual to regard Ecology as a very recent development of botanical science, but Nehemiah Grew seems to have been alive to the importance of the ecological standpoint,—though he did not describe it by this name. He writes "The proper Places also of Plants, or such wherein they have…a Spontaneous growth, should be considered. And that as to the Climate; whether in one Colder, Temperate, or more Hot. The Region; Continent, or Island. The Seat: as Sea, or Land, Watry, Boggy, or Dry; Hills, Plains, or Vallies; Open, in Woods, or under Hedges; against Walls, rooted in them, or on their Tops; and the like."
Crew's most interesting contribution to science was, perhaps, his publication of the fact that the flowering plants, like animals, shew the phenomena of sex. He never, however, actually proved this contention in an experimental way. At the time that his earliest work was published, he was frankly puzzled by the stamens, or, as he calls them, the "Attire." He recognised their use to insects, to whom flowers serve, in his own words, as "their Lodging and their Dining-Room." He also fully realised their value to man as increasing the beauty of the blossom, but he was broad-minded enough to feel that these must be secondary uses, and that "the primary and private use of the attire" remained to be discovered. Ten years later, in the second edition of his work, he tells us that it was suggested to him in conversation by Sir Thomas Millington that the stamens were the male organs. It seems probable that, although Grew gives Millington the credit for this discovery, he had really arrived at it independently, for he tells us that when Millington made the suggestion, he "immediately reply'd that [he] was of the same Opinion; and gave him some reasons for it, and answered some Objections, which might oppose them."
Besides his belief in the male nature of the stamen, Nehemiah Grew came to some rather mysterious conclusions as to their serving to draw off the redundant part of the sap, not needed to produce the seed. He also used the word "attire" for the florets of the Compositae, but qualified it by calling the stamens the "seminal attire," and the florets of compound flowers the "florid attire." He says that "every Flower with the Florid attire" (or, as we should now say, "every composite flower") "Embosomes, or is, a Posy of perfect Flowers." He recognised the "globulets" (pollen grains) as being of the same nature as those in the anthers of simple flowers. He describes the disk florets with remarkable accuracy, but falls into the error of supposing that the pollen grains are in some cases originally produced by the style and stigmas, which he calls the "Blade," and which he did not recognise as part of the female organ. His figures make it clear that he mistook the stylar hairs for little stalks organically connecting the pollen grains and the style. In other cases, however, he observed that the pollen grains occurred on the inner side of what we now know as the staminal tube.
Grew enters into considerable detail as regards the structure of flowers, and it is only possible to mention here a few of the points to which he draws attention. He observed the frequent occurrence of capitate glandular hairs, which he describes as "like so many little Mushrooms sprouting out of the Flower," their heads sometimes exuding a "Gummy or Balsamick Juyce." He describes the varieties of aestivation of the floral leaves, and notes that, in the Poppy, the large size and fewness of the petals prevents their being folded into a compacy body by any of the ordinary methods. "For which reason, they are cramb'd up within the Empalement by hundreds of little Wrinckles or Puckers; as if Three or Four Fine Cambrick Handcherchifs were thrust into ones Pocket."
We have said something about Grew's work on seeds, in dealing with his first treatise. He was always much interested in this subject, and returned to it again in his later work. He mentions the mucilaginous testa possessed by many seeds, but which only becomes noticeable when they have been moistened. That of "Nasturtium Hortense" he describes as very large, "even emulous of the inner Pulp surrounding a Gooseberry-Seed." He suggests that the value of putting a Clary seed into the eye to bring out a foreign body, which may have lodged there, is due to the presence of the mucilaginous coat. The same seed is still, I believe, used for this purpose, under the name of "eye seed." Grew understood the difference between seeds with, and without endosperm, and gives perfectly clear representations of such albuminous seeds as Ricimis. He describes the cotyledons of the Dock as being immersed in the endosperm, "as in a Tub of Meal or a little pot of pure refin'd Mould, necessary for the first Vegetation of the Radicle."
Grew naturally reckoned the spores of Ferns among seeds. The seed-case of the Harts-tongue is, he says, "of a Silver Colour…of a spherick Figure, and girded about with a sturdy Tendon or Spring, of the Colour of Gold:… So soon as… this Spring is become stark enough, it suddenly breaks the Case into two halfs, like two little cups, and so flings the Seed," of which "ten Thousand are not so big as a white Pepper Corn."
To give any kind of short summary of Grew's botanical work is well-nigh impossible. Some men are remembered for individual discoveries, and in such cases it is not difficult to give a précis of their contributions. But Nehemiah Grew is remembered because, contemporaneously with Malpighi, he actually created the science of plant anatomy,—a subject which, before his day, was practically non-existent. Modern botanists, conscious how small an addition to the fabric is now regarded as a satisfactory life-work, must stand amazed and somewhat humbled before the broad and sound foundations laid by this seventeenth century physician. It is no less than two hundred and forty years since Grew sent in his first treatise to the Royal Society, so it is scarcely wonderful that a number of his results have been rejected in course of time. It is far more remarkable that so many of his conclusions—and those the more essential ones—have been merely confirmed and extended by later work. Great however as were his actual contributions to botanical knowledge, they were perhaps less important than the far-reaching service which he rendered in helping to free biological thought from the cramping belief that the one and only object of the existence of the organic world was for the use and pleasure of man. Grew believed that the "Outward Elegancies of Plants" might be for the purpose of giving delight to the human race, but he was the first to point out that as the "Inward Ones, which, generally, are as Precise and Various as the Outward," are so seldom seen, their purpose can hardly be for this, but must be for the benefit of the plants themselves, "That the Corn might grow, so; and the Flower, so, whether or no Men had a mind, leisure, or ability, to understand how."
- Dict. Nat. Biog., edited by Leslie Stephen and Sidney Lee, vol. XXIII. 1890.
- Enoch's Translation. A Funeral Sermon Upon the Sudden Death of Dr Nehemiah Grew, Fellow of the College of Physicians. Who died March 25th, 1712. Preach'd at Old-Jewry. By John Shower. London. 1712.
- Life of Robert Boyle by Thomas Birch, p. 83, 1744.
- M. J. Schleiden, Grundzüge der wissenschaftlichen Botanik, Vol. 1. p. 198, 1842. The incorrect statement that Grew was Secretary of the Royal Society at the time that Malpighi's manuscript was received by that body, is also repeated in the English translation of Schleiden's work [Schleiden's Principles of Scientific Botany, translated by Edwin Lankester, London, 1849, p. 38].
- Aloys Pollender, Wem gebührt die Priorität in der Anatomie der Pflanzen dem Grew oder dem Malpighi? Bonn, 1868.
- Marcellus Malpighi, Anatome Plantarum, 2 pts, London, 1875 and 1879 (see also Marcellus Malpighi, Die Anatomie der Pflanzen, Bearbeitet von M. Mobius, Leipzig, 1901. In this little book the more important parts of Malpighi's work are translated into German, and a number of the figures reproduced).
- The order of the paragraphs is slightly altered from that of the original.
- By the courtesy of the Council of the Royal Society, I have been able to compare these annotations with certain manuscript letters of Nehemiah Grew's preserved in the Society's Library. This comparison confirms the view that the annotations are in Grew's own handwriting.
- Manchet = a loaf of fine wheaten bread. (An Etymological Dictionary of the English Language. W. W. Skeat. New ed. 1910.)
- Medullary rays.
- Ernst H. F. Meyer, Geschichte der Botanik, vol iv. p. 60, 1857.
- M. Westermaier, "Zur Kenntniss der osmotischen Leistungen des lebenden Parenchym's." Ber. d. deutsch. bot. Gesellsch. Bd 1. p. 371,1883.
- The Anatomy of Vegetables Begun, 1672.