1: In our own National Gallery. It is quaint and imperfect, but of great interest.
1: In our own National Gallery. It is quaint and imperfect, but of great interest.
CHAPTER II.
THE LEAF ORDERS.
§ 1. Asin our sketch of the structure of mountains it seemed advisable to adopt a classification of their forms, which, though inconsistent with absolute scientific precision, was convenient for order of successive inquiry, and gave useful largeness of view; so, and with yet stronger reason, in glancing at the first laws of vegetable life, it will be best to follow an arrangement easily remembered and broadly true, however incapable of being carried out into entirely consistent detail. I say, “with yet stronger reason,” because more questions are at issue among botanists than among geologists; a greater number of classifications have been suggested for plants than for rocks; nor is it unlikely that those now accepted may be hereafter modified. I take an arrangement, therefore, involving no theory; serviceable enough for all working purposes, and sure to remain thus serviceable, in its rough generality, whatever views may hereafter be developed among botanists.
§ 2. A child’s division of plants is into “trees and flowers.” If, however, we were to take him in spring, after he had gathered his lapful of daisies, from the lawn into the orchard, and ask him how he would call those wreaths of richer floret, whose frail petals tossed their foam of promise between him and the sky, he would at once see the need of some intermediate name, and call them, perhaps, “tree-flowers.” If, then, we took him to a birch-wood, and showed him that catkins were flowers, as well as cherry-blossoms, he might, with a little help, reach so far as to divide all flowers into two classes; one, those that grew on ground; and another, those that grew on trees. The botanist might smile at such a division; but an artist would not. To him, as the child, there is something specific and distinctive in those rough trunks that carry the higher flowers. To him, itmakes the main difference between one plant and another, whether it is to tell as a light upon the ground, or as a shade upon the sky. And if, after this, we asked for a little help from the botanist, and he were to lead us, leaving the blossoms, to look more carefully at leaves and buds, we should find ourselves able in some sort to justify, even to him, our childish classification. For our present purposes, justifiable or not, it is the most suggestive and convenient. Plants are, indeed, broadly referable to two great classes. The first we may, perhaps, not inexpediently callTENTED PLANTS. They live in encampments, on the ground, as lilies; or on surfaces of rock, or stems of other plants, as lichens and mosses. They live—some for a year, some for many years, some for myriads of years; but, perishing, they pass as the tented Arab passes; they leaveno memorials of themselves, except the seed, or bulb, or root which is to perpetuate the race.
§ 3. The other great class of plants we may perhaps best callBUILDING PLANTS. These will not live on the ground, but eagerly raise edifices above it. Each works hard with solemn forethought all its life. Perishing, it leaves its work in the form which will be most useful to its successors—its own monument, and their inheritance. These architectural edifices we call “Trees.”
It may be thought that this nomenclature already involves a theory. But I care about neither the nomenclature, nor about anything questionable in my description of the classes. The reader is welcome to give them what names he likes, and to render what account of them he thinks fittest. But to us, as artists, or lovers of art, this is the first and most vital question concerning a plant: “Has it a fixed form or a changing one? Shall I find it always as I do to-day—this Parnassia palustris—with one leaf and one flower? or may it some day have incalculable pomp of leaves and unmeasured treasure of flowers? Will it rise only to the height of a man—as an ear of corn—and perish like a man; or will it spread its boughs to the sea and branches to the river, and enlarge its circle of shade in heaven for a thousand years?”
§ 4. This, I repeat, is thefirstquestion I ask the plant. And as it answers, I range it on one side or the other, amongthose that rest or those that toil: tent-dwellers, who toil not, neither do they spin; or tree-builders, whose days are as the days of the people. I find again, on farther questioning these plants who rest, that one group of them does indeed rest always, contentedly, on the ground, but that those of another group, more ambitious, emulate the builders; and though they cannot build rightly, raise for themselves pillars out of the remains of past generations, on which they themselves, living the life of St. Simeon Stylites, are called, by courtesy, Trees; being, in fact, many of them (palms, for instance) quite as stately as real trees.1
These two classes we might call earth-plants, and pillar-plants.
§ 5. Again, in questioning the true builders as to their modes of work, I find that they also are divisible into two great classes. Without in the least wishing the reader to accept the fanciful nomenclature, I think he may yet most conveniently remember these as “Builders with the shield,” and “Builders with the sword.”
Builders with the shield have expanded leaves, more or less resembling shields, partly in shape, but still more in office; for under their lifted shadow the young bud of the next year is kept from harm. These are the gentlest of the builders, and live in pleasant places, providing food and shelter for man. Builders with the sword, on the contrary, have sharp leaves in the shape of swords, and the young buds, instead of being as numerous as the leaves, crouching each under a leaf-shadow, are few in number, and grow fearlessly, each in the midst of a sheaf of swords. These builders live in savage places, are sternly dark in color, and though they give much help to man by their merely physical strength, they (with few exceptions) give him no food, and imperfect shelter. Their mode of building is ruder than that ofthe shield-builders, and they in many ways resemble the pillar-plants of the opposite order. We call them generally “Pines.”
§ 6. Our work, in this section, will lie only among the shield-builders, sword-builders, and plants of rest. The Pillar-plants belong, for the most part, to other climates. I could not analyze them rightly; and the labor given to them would be comparatively useless for our present purposes. The chief mystery of vegetation, so far as respects external form, is among the fair shield-builders. These, at least, we must examine fondly and earnestly.
1I am not sure that this is a fair account of palms. I have never had opportunity of studying stems of Endogens, and I cannot understand the description given of them in books, nor do I know how far some of their branched conditions approximate to real tree-structure. If this work, whatever errors it may involve, provokes the curiosity of the reader so as to lead him to seek for more and better knowledge, it will do all the service I hope from it.
1I am not sure that this is a fair account of palms. I have never had opportunity of studying stems of Endogens, and I cannot understand the description given of them in books, nor do I know how far some of their branched conditions approximate to real tree-structure. If this work, whatever errors it may involve, provokes the curiosity of the reader so as to lead him to seek for more and better knowledge, it will do all the service I hope from it.
CHAPTER III.
THE BUD.
§ 1. Ifyou gather in summer time an outer spray of any shield-leaved tree, you will find it consists of a slender rod, throwing out leaves, perhaps on every side, perhaps on two sides only, with usually a cluster of closer leaves at the end. In order to understand its structure, we must reduce it to a simple general type. Nay, even to a very inaccurate type. For a tree-branch is essentially a complex thing, and no “simple” type can, therefore, be a right one.
This type I am going to give you is full of fallacies and inaccuracies; but out of these fallacies we will bring the truth, by casting them aside one by one.
§ 2. Let the tree spray be represented under one of these two types,AorB, Fig. 1, the cluster at the end being in each case supposed to consist of three leaves only (a most impertinent supposition, for it must at least have four, only the fourth would be in a puzzling perspective inA, and hidden behind the central leaf inB). So, receive this false type patiently. When leaves are set on the stalk one after another, as inA, they are called “alternate;” when placed as inB, “opposite.” It is necessary you should remember this not very difficult piece of nomenclature.
If you examine the branch you have gathered, you will see that for some little way below the full-leaf cluster at the end, the stalk is smooth, and the leaves are set regularly on it. But at six, eight, or ten inches down, there comes an awkward knot;something seems to have gone wrong, perhaps another spray branches off there; at all events, the stem gets suddenly thicker, and you may break it there (probably) easier than anywhere else.
That is the junction of two stories of the building. The smooth piece has all been done this summer. At the knot the foundation was left during the winter.
The year’s work is called a “shoot.” I shall be glad if you will break it off to look at; as myAandBtypes are supposed to go no farther down than the knot.
The alternate formAis more frequent thanB, and some botanists think includesB. We will, therefore, begin with it.
§ 3. If you look close at the figure, you will see small projecting points at the roots of the leaves. These represent buds, which you may find, most probably, in the shoot you have in your hand. Whether you find them or not, they are there—visible, or latent, does not matter. Every leaf has assuredly an infant bud to take care of, laid tenderly, as in a cradle, just where the leaf-stalk forms a safe niche between it and the main stem. The child-bud is thus fondly guarded all summer; but its protecting leaf dies in the autumn; and then the boy-bud is put out to rough winter-schooling, by which he is prepared for personal entrance into public life in the spring.
Let us suppose autumn to have come, and the leaves to have fallen. Then ourAof Fig. I, the buds only being left, one for each leaf, will appear asA B, in Fig. 2. We will call the buds grouped atB, terminal buds, and those ata,b, andc, lateral buds.
This budded rod is the true year’s work of the building plant, at that part of its edifice. You may consider the little spray, if you like, as one pinnacle of the tree-cathedral, which has taken a year to fashion; innumerable other pinnacles having been built at the same time on other branches.
§ 4. Now, every one of these buds,a,b, andc, as well as every terminal bud, has the power and disposition to raise himself in the spring, into just such another pinnacle asA Bis.
This development is the process we have mainly to study in this chapter; but, in the outset, let us see clearly what it is to end in.
Each bud, I said, has the power and disposition to make a pinnacle of himself, but he has not always the opportunity. What may hinder him we shall see presently. Meantime, the reader will, perhaps, kindly allow me to assume that the budsa,b, andc, come to nothing, and only the three terminal ones build forward. Each of these producing the image of the first pinnacle, we have the type for our next summer bough of Fig. 3; in which observe the original shootA B, has become thicker; its lateral buds having proved abortive, are now only seen as little knobs on its sides. Its terminal buds have each risen into a new pinnacle. The central or strongest oneB C, has become the very image of what his parent shootA B, was last year. The two lateral ones are weaker and shorter, one probably longer than the other. The joint atBis the knot or foundation for each shoot above spoken of.
Knowing now what we are about, we will go into closer detail.
§ 5. Let us return to the type in Fig. 2, of the fully accomplished summer’s work: the rod with its bare buds. Plate 51, opposite, represents, of about half its real size, an outer spray of oak in winter. It is not growing strongly, and is as simple as possible in ramification. You may easily see, in each branch, the continuous piece of shoot produced last year. The wrinkles which make these shoots look like old branches are caused by drying, as the stalk of a bunch of raisins is furrowed (the oak-shoot fresh gathered isround as a grape-stalk). I draw them thus, because the furrows are important clues to structure. Fig. 4 is the top of one of these oak sprays magnified for reference. The little brackets,x,y, &c., which project beneath each bud and sustain it, are the remains of the leaf-stalks. Those stalks were jointed at that place, and the leaves fell without leaving a scar, only a crescent-shaped, somewhat blank-looking flat space, which you may study at your ease on a horse-chestnut stem, where these spaces are very large.
§ 6. Now if you cut your oak spray neatly through, just above a bud, as atA, Fig. 4, and look at it with a not very powerful magnifier, you will find it present the pretty section, Fig. 5.
That is the proper or normal section of an oak spray. Never quite regular. Sure to have one of the projections a little larger than the rest, and to have its bark (the black line) not quite regularly put round it, but exquisitely finished, down to a little white star in the very centre, which I have not drawn, because it would look in the woodcut black, not white; and be too conspicuous.
The oak spray, however, will not keep this form unchanged for an instant. Cut it through a little way above your first section, and you will find the largest projection is increasing till, just where it opens1at last into the leaf-stalk, its section is Fig. 6. If, therefore, you choose to consider every interval between bud and bud as one story of your tower or pinnacle, you find that there is literally not a hair’s-breadth of the work in which theplanof the tower does not change. You may see in Plate 51 that every shoot is suffused by a subtle (innature aninfinitelysubtle) change of contour between bud and bud.
§ 7. But farther, observe in what succession those buds are put round the bearing stem. Let the section of the stem be represented by the small central circle in Fig. 8; and suppose it surrounded by anearlyregular pentagon (in the figure it is quite regular for clearness’ sake). Let the first of any ascending series of buds be represented by the curved projection filling the nearest angle of the pentagon at 1. Then the next bud, above, will fill the angle at 2; the next above, at 3, the next at 4, the next at 5. The sixth will come nearly over the first. That is to say, each projecting portion of the section, Fig. 5, expands into its bud, not successively, but by leaps, always to thenext but one;the buds being thus placed in a nearly regular spiral order.
§ 8. I say nearly regular—for there are subtleties of variation in plan which it would be merely tiresome to enter into. All that we need care about is the general law, of which the oak spray furnishes a striking example,—that the buds of the first great group of alternate builders rise in a spiral order round the stem (I believe, for the most part, the spiral proceeds from right to left). And this spiral succession very frequently approximates to the pentagonal order, which it takes with great accuracy in an oak; for, merely assuming that each ascending bud places itself as far as it can easily out of the way of the one beneath, and yet not quite on the opposite side of the stem, we find the interval between the two must generally approximate to that left between 1 and 2, or 2 and 3, in Fig. 8.2
§ 9. Should the interval be consistently a littlelessthan that which brings out the pentagonal structure, the plant seems to get at first into much difficulty. For, in such case, there is a probability of the buds falling into a triangle, as atA, Fig. 9; and then the fourth must come over the first, which would be inadmissible (we shall soon see why). Nevertheless, the plant seems to like the triangular result for its outline, and sets itself to get out of the difficulty with much ingenuity, by methods of succession, which I will examine farther in the next chapter: it being enough for us to know at present that the puzzled, but persevering, vegetabledoesget out of its difficulty and issues triumphantly, and with a peculiar expression of leafy exultation, in a hexagonal star, composed of two distinct triangles, normally as atB, Fig. 9. Why the buds do not like to be one above the other, we shall see in next chapter. Meantime I must shortly warn the reader of what we shall then discover, that, though we have spoken of the projections of our pentagonal tower as if they were first built to sustain each its leaf, they are themselves chiefly built by the leaf they seem to sustain. Without troubling ourselves about this yet, let us fix in our minds broadly the effective aspect of the matter, which is all we want, by a simple practical illustration.
§ 10. Take a piece of stick half-an-inch thick, and a yard or two long, and tie large knots, at anyequaldistances you choose, on a piece of pack-thread. Then wind the pack-thread round the stick, with any number of equidistant turns you choose, from one end to the other, and the knots will take the position of buds in the general type of alternate vegetation. By varying the number of knots and the turns of the thread, you may get the system of any tree, with the exception of one character only—viz., that since the shoot grows faster at one time than another, the buds run closer together when the growth is slow. You cannot imitate this structure by closing the coils of your string, for that would alter the positions of your knots irregularly. The intervals between the buds are, by this gradual acceleration or retardation of growth, usually varied in lovely proportions. Fig.10 shows the elevations of the buds on five different sprays of oak;AandBbeing of the real size (short shoots);C,D, andE, on a reduced scale. I have not traced the cause of the apparent tendency of the buds to follow in pairs, in these longer shoots.
§ 11. Lastly: If the spiral be constructed so as to bring the buds nearly on opposite sides of the stem, though alternate in succession, the stem, most probably, will shoot a little away from each bud after throwing it off, and thus establish the oscillatory formb, Fig. 11, which, when the buds are placed, as in this case, at diminishing intervals, is very beautiful.3
§ 12. I fear this has been a tiresome chapter; but it is necessary to master the elementary structure, if we are to understand anything of trees; and the reader will therefore, perhaps, take patience enough to look at one or two examples of the spray structure of the second great class of builders, in which the leaves are opposite. Nearly all opposite-leaved trees grow, normally, like vegetable weathercocks run to seed, with north and south, and east and west pointers thrown off alternately one over another, as in Fig. 12.
This, I say, is the normal condition. Under certain circumstances, north and south pointers set themselves north-east and south-west; this concession being acknowledged and imitated by the east and west pointers at the next opportunity; but, for the present, let us keep to our simple form.
The first business of the budding stem, is to get every pair of buds set accurately at right angles to the one below. Here are some examples ofthe way it contrives this.A, Fig. 13, is the section of the stem of a spray of box, magnified eight or nine times, just where it throws off two of its leaves, suppose on north and south sides. The crescents below and above are sections through the leaf-stalks thrown off on each side. Just above this joint, the section of the stem isB, which is the normal section of a box-stem, as Fig. 5 is of an oak’s. This, as it ascends, becomesC, elongating itself now east and west; and the section next toC, would be again A turned that way; or, taking the succession completely through two joints, and of the real size, it would be thus: Fig. 14.
The stem of the spotted aucuba is normally hexagonal, as that of the box is normally square. It is very dexterous and delicate in its mode of transformation to the two sides. Through the joint it isA, Fig. 15. Above joint,B, normal, passing on intoC, andDfor the next joint.
While in the horse-chestnut, a larger tree, and, as we shall see hereafter, therefore less regular in conduct, the section, normally hexagonal, is much rounded and softened into irregularities;A, Fig. 16, becoming, as it buds,BandC. The dark diamond besideCis a section through a bud, in which, however small, the quatrefoil disposition is always seen complete: the four little infant leaves with a queen leaf in the middle, all laid in their fan-shaped feebleness, safe in a white cloud of miniature woollen blanket.
§ 13. The elementary structure of all important trees may, I think, thus be resolved into three principal forms: three-leaved, Fig. 9; four-leaved, Figs. 13 to 16; and five-leaved, Fig. 8. Or, in well-known terms, trefoil, quatrefoil, cinqfoil. And these are essential classes, more complicated forms being usually, it seems to me, resolvable into these, but these not into each other. The simplest arrangement (Fig. 11), in which the buds are nearly opposite in position, though alternate in elevation, cannot, I believe, constitute a separate class, being only an accidental condition of the spiral. If it did, it might be called difoil; but the important classes are three:—
§ 14. The coincidences between beautiful architecture and the construction of trees must more and more have become marked in the reader’s mind as we advanced; and if he will now look at what I have said in other places of the use and meaning of the trefoil, quatrefoil, and cinqfoil, in Gothic architecture, hewill see why I could hardly help thinking and speaking of all trees as builders. But there is yet one more subtlety in their way of building which we have not noticed. If the reader will look carefully at the separate shoots in Plate 51, he will see that the furrows of the stems fall in almost every case into continuous spiral curves, carrying the whole system of buds with them. This superinduced spiral action, of which we shall perhaps presently discover the cause, often takes place vigorously, producing completely twisted stems of great thickness. It is nearly always existent slightly, giving farther grace and change to the whole wonderful structure. And thus we have, as the final result of one year’s vegetative labor on any single spray, a twisted tower, not similar at any height of its building: or (for, as we shall see presently, it loses in diameter at each bud) a twisted spire, correspondent somewhat in principle to the twisted spire of Dijon, or twisted fountain of Ulm, or twisted shafts of Verona. Bossed as it ascends with living sculpture, chiselled, not by diminution but through increase, it rises by one consistent impulse from its base to its minaret, ready, in spring-time, to throw round it at the crest at once the radiance of fresh youth and the promise of restoration after that youth has passed away. A marvellous creation: nay might we not almost say, a marvellous creature full of prescience in its infancy, foreboding even, in the earliest gladness of its opening to sunshine, the hour of fainting strength and falling leaf, and guarding under the shade of its faithful shields the bud that is to bear its hope through winter’s shieldless sleep?
Men often look to bring about great results by violent and unprepared effort. But it is only in fair and forecast order, “as the earth bringeth forth her bud,” that righteousness and praise may spring forth before the nations.
1The added portion, surrounding two of the sides of the pentagon, is the preparation for the stalk of the leaf, which, on detaching itself from the stem, presents variable sections, of which those numbered 1 to 4, Fig. 7, are examples. I cannot determine the proper normal form. The bulb-shaped spot in the heart of the uppermost of the five projections in Fig. 6 is the root of the bud.2For more accurate information the reader may consult Professor Lindley’sIntroduction to Botany(Longman, 1848), vol. i. p. 245,et seqq.3Fig. 11 is a shoot of the line, drawn on two sides, to show its continuous curve in one direction, and alternated curves in another. The buds, which may be seen to be at equal heights in the two figures, are exquisitely proportioned in their distances. There is no end to the refinement of system, if we choose to pursue it.
1The added portion, surrounding two of the sides of the pentagon, is the preparation for the stalk of the leaf, which, on detaching itself from the stem, presents variable sections, of which those numbered 1 to 4, Fig. 7, are examples. I cannot determine the proper normal form. The bulb-shaped spot in the heart of the uppermost of the five projections in Fig. 6 is the root of the bud.
2For more accurate information the reader may consult Professor Lindley’sIntroduction to Botany(Longman, 1848), vol. i. p. 245,et seqq.
3Fig. 11 is a shoot of the line, drawn on two sides, to show its continuous curve in one direction, and alternated curves in another. The buds, which may be seen to be at equal heights in the two figures, are exquisitely proportioned in their distances. There is no end to the refinement of system, if we choose to pursue it.
CHAPTER IV.
THE LEAF.
§ 1. Havingnow some clear idea of the position of the bud, we have next to examine the forms and structure of its shield—the leaf which guards it. You will form the best general idea of the flattened leaf of shield-builders by thinking of it as you would of a mast and sail. More consistently with our classification, we might perhaps say, by thinking always of the arm sustaining the shield; but we should be in danger of carrying fancy too far, and the likeness of mast and sail is closer, for the mast tapers as the leaf-rib does, while the hand holding the uppermost strap of the buckler clenches itself. Whichever figure we use, it will cure us of the bad habit of imagining a leaf composed of a short stalk with a broad expansion at the end of it. Whereas we should always think of the stalk as running right up the leaf to its point, and carrying the expanded, or foliate part, as the mast of a lugger does its sail. To some extent, indeed, it has yards also, ribs branching from the innermost one; only the yards of the leaf will not run up and down, which is one essential function of a sailyard.
§ 2. The analogy will, however, serve one step more. As the sail must be on one side of the mast, so the expansion of a leaf is on one side of its central rib, or of its system of ribs. It is laid over them as if it were stretched over a frame, so that on the upper surface it is comparatively smooth; on the lower, barred. The understanding of the broad relations of these parts is the principal work we have to do in this chapter.
§ 3. First, then, you may roughly assume that the section of any leaf-mast will be a crescent, as ata, Fig. 17 (compare Fig. 7 above). The flat side is the uppermost, the round side underneath, and the flat or upper side caries the leaf. You can at once see the convenience of this structure for fitting to a centralstem. Suppose the central stem has a little hole in the centre,b, Fig. 17, and that you cut it down through the middle (as terrible knights used to cut their enemies in the dark ages, so that half the head fell on one side, and half on the other): Pull the two halves separate,c, and they will nearly represent the shape and position of opposite leaf-ribs. In reality the leaf-stalks have to fit themselves to the central stem,a, and as we shall see presently, to lap round it: but we must not go too fast.
§ 4. Now,a, Fig. 17, being the general type of a leaf-stalk, Fig. 18 is the general type of the way it expands into and carries its leaf;1this figure being the enlargement of a typical section right across any leaf, the dotted lines show the under surface foreshortened. You see I have made one side broader than the other. I mean that. It is typically so. Nature cannot endure two sides of a leaf to be alike. By encouraging one side more than the other, either by giving it more air or light, or perhaps in a chief degree by the mere fact of the moisture necessarily accumulating on the lower edge when it rains, and the other always drying first, she contrives it so, that if the essential form or idea of the leaf bea, Fig. 19, the actual form will always bec, or an approximate to it;one half being pushed in advance of the other, as atb, and all reconciled by soft curvature,c. The effort of the leaf to keep itself symmetrical rights it, however, often at the point, so that the insertion of the stalk only makes the inequality manifest. But it follows that the sides of a straight section across the leaf are unequal all the way up, as in my drawing, except at one point.
§ 5. I have represented the two wings of the leaf as slightly convex on the upper surface. This is also on the whole a typical character. I use the expression “wings of the leaf,” because supposing we exaggerate the main rib a little, the section will generally resemble a bad painter’s type of a bird (a, Fig. 20). Sometimes the outer edges curl up,b, but an entirely concave form,c, is rare. Whenbis strongly developed, closing well in, the leaf gets a good deal the look of a boat with a keel.
§ 6. If now you take this oblique form of sail, and cut it into any number of required pieces down to its mast, as in Fig. 21,A, and then suppose each of the pieces to contract into studding-sails at the side, you will have whatever type of divided leaf you choose to shape it for. In Fig. 21,A,B, I have taken the rose as the simplest type. The leaf is given in separate contour atC; butthat of the mountain ash,A, Fig. 22, suggests the original oval form which encloses all the subdivisions much more beautifully. Each of the studding-sails in this ash-leaf looks much at first as if he were himself a mainsail. But you may know him always to be a subordinate, by observing that the inequality of the two sides which is brought about by accidental influences in the mainsail, is an organic law in the studding-sail. The real leaf tries to set itself evenly on its mast; and the inequality is only a graceful concession to circumstances. But the subordinate or studding-sail is alwaysby lawlarger at one side than the other; and if he is himself again divided into smaller sails, he will have larger sails on the lowest side, or one more sail on the lowest side, than he has on the other. He always wears, therefore, a servant’s, or, at least, subordinate’s dress. You may know him anywhere as not the master. Even in the ash leaflet, of which I have outlined one separately,B, Fig. 22, this is clearly seen; but it is much more distinct in more finely divided leaves.2
§ 7. Observe, then, that leaves are broadly divisible into mainsails and studding-sails; but that the wordleafis properly to be used only of the mainsail; leaflet is the best word for minor divisions; and whether these minor members are only separated by deep cuts, or become complete stalked leaflets, still they are always to be thought of merely as parts of a true leaf.
It follows from the mode of their construction that leaflets must always lie more or lessflat, or edge to edge, in a continuous plane. This position distinguishes them from true leaves as much as their oblique form, and distinguishes them with the same delicate likeness of system; for as the true leaf takes, accidentally and partially, the oblique outline which is legally required in the subordinate, so the true leaf takes accidentally and partially the flat disposition which is legally required in the subordinate. And this point of position we must now study. Henceforward, throughout this chapter, the reader will please note that I speak only of trueleaves, not ofleaflets.
§ 8. LAW I.The Law of Deflection.—The first law, then, respecting position in true leaves, is that they fall gradually back from the uppermost one, or uppermost group. They are never set as ata, Fig. 23, but always as atb. The reader may see at once that they have more room and comfort by means of the latter arrangement. The law is carried out with more or less distinctness according to the habit of the plant; but is always acknowledged.
In strong-leaved shrubs or trees it is shown with great distinctness and beauty: the phillyrea shoot, for instance, Fig. 24, is almost in as true symmetry as a Greek honeysuckle ornament.In the hawthorn shoot, central in Plate 52, opposite, the law is seen very slightly, yet it rules all the play and fantasy of the varied leaves, gradually depressing their lines as they are set lower. In crowded foliage of large trees the disposition of each separate leaf is not so manifest. For there is a strange coincidence in this between trees and communities of men. When the community is small, people fall more easily into their places, and take, each in his place, a firmer standing than can be obtained by the individuals of a great nation. The members of a vast community are separately weaker, as an aspen or elm leaf is thin, tremulous, and directionless, compared with the spear-like setting and firm substance of a rhododendron or laurel leaf. The laurel and rhododendron are like the Athenian or Florentine republics; the aspen like England—strong-trunked enough when put to proof, and very good for making cartwheels of, but shaking pale with epidemic panic at every breeze. Nevertheless, the aspen has the better of the great nation, in that if you take it bough by bough, you shall find the gentle law of respect and room for each other truly observed by the leaves in such broken way as they can manage it; but in the nation you find every one scrambling for his neighbor’s place.
This, then, is our first law, which we may generally call the Law of Deflection; or, if the position of the leaves with respect to the root be regarded, of Radiation. The second is more curious, and we must go back over our ground a little to get at it.
§ 9. LAW II.The Law of Succession.—From what we saw of the position of buds, it follows that in every tree the leaves at the end of the spray, taking the direction given them by the uppermost cycle or spiral of the buds, will fall naturally into a starry group, expressive of the order of their growth. In an oak we shall have a cluster of five leaves, in a horse-chestnut of four, in a rhododendron of six, and so on. But observe, if we draw the oak-leaves all equal, as ata, Fig. 25, or the chestnut’s (b), or the rhododendron’s (c), you instantly will feel, or ought to feel, that something is wrong; that those are not foliage forms—not even normally or typically so—but dead forms, like crystals of snow. Considering this, and looking back to last chapter, you will see that the buds which throw out these leaves do not grow side by side, but one above another. In the oak and rhododendron,all five and all six buds are at different heights; in the chestnut, one couple is above the other couple.
§ 10. Now so surely as one bud is above another, it must be stronger or weaker than that other. The shoot may either be increasing in strength as it advances, or declining; in either case, the buds must vary in power, and the leaves in size. At the top of the shoot, the last or uppermost leaves are mostly the smallest; of course always so in spring as they develope.
Let us then apply these conditions to our formal figure above, and suppose each leaf to be weaker in its order of succession. The oak becomes asa, Fig. 26, the chestnut shoot asb, the rhododendron,c. These, I should think, it can hardly be necessary to tell the reader, are true normal forms;—respecting which one or two points must be noticed in detail.
§ 11. The magnitude of the leaves in the oak star diminishes, of course, in alternate order. The largest leaf is the lowest, 1 in Figure 8, p. 14. While the largest leaf forms the bottom, next it, opposite each other, come the third and fourth, in order and magnitude, and the fifth and second form the top. An oak staris, therefore, always an oblique star; but in the chestnut and other quatrefoil trees, though the uppermost couple of leaves must always be smaller than the lowermost couple, there appears no geometrical reason why the opposite leaves of each couple should vary in size. Nevertheless, they always do, so that the quatrefoil becomes oblique as well as the cinqfoil, as you see it is in Fig. 26.
The normal of four-foils is therefore as in Fig. 27,A(maple): with magnitudes, in order numbered; but it often happens that an opposite pair agree to become largest and smallest; thus giving the pretty symmetry, Fig. 27,B(spotted aucuba). Of coursethe quatrefoil in reality is always less formal, one pair of leaves more or less hiding or preceding the other. Fig. 28 is the outline of a young one in the maple.
§ 12. The third form is more complex, and we must take the pains to follow out what we left unobserved in last chapter respecting the way a triplicate plant gets out of its difficulties.
Draw a circle as in Fig. 29, and two lines,AB,BC, touching it, equal to each other, and each divided accurately in half where they touch the circle, so thatAPshall be equal toPB,BQ, andQC. And let the linesABandBCbe so placed that a dotted lineAC, joining their extremities, would not be much longer than either of them.
Continue to draw lines of the same length all round the circle. Lay five of them,AB,BC,CD,DE,EF. Then join the pointsAD,EB, andCF, and you have Fig. 30, which is a hexagon, with the following curious properties. It has one side largest,CD, two sides less, but equal to each other,AEandBF; and three sides less still, and equal to each other,AD,CF, andBE.
Now put leaves into this hexagon, Fig. 31, and you will see how charmingly the rhododendron has got out of its difficulties. The next cycle will put a leaf in at the gap at the top, and begin a new hexagon. Observe, however, this geometrical figure is only to the rhododendron what theain Fig. 25 is to the oak, theicy or dead form. To get the living normal form we must introduce our law of succession. That is to say, the five linesAB,BC, &c., must continually diminish, as they proceed, and therefore continually approach the centre; roughly, as in Fig. 32.
§ 13. I dread entering into the finer properties of this construction, but the reader cannot now fail to feel their beautiful result either in the cluster in Fig. 26, or here in Fig. 33, which is a richer and more oblique one. The three leaves of the uppermost triad are perfectly seen, closing over the bud; and the general form is clear, though the lower triads are confused to the eye by unequal development, as in these complex arrangements is almost always the case. The more difficulties are to be encountered the more licence is given to the plant in dealing with them, and we shall hardly ever find a rhododendron shoot fulfilling its splendid spiral as an oak does its simple one.
Here, for instance, is the actual order of ascending leaves in four rhododendron shoots which I gather at random.
Of these,Ais the only quite well-conducted one;Btakes one short step,C, one step backwards, andD, two steps back and one, too short, forward.
§ 14. LAW III.The Law of Resilience.—If you havebeen gathering any branches from the trees I have named among quatrefoils (the box is the best for exemplification), you have perhaps been embarrassed by finding that the leaves, instead of growing on four sides of the stem, did practically grow oppositely on two. But if you look closely at the places of their insertion, you will find they indeed spring on all four sides; and that in order to take the flattened opposite position, each leaf twists round on its stalk, as in Fig. 35, which represents a box-leaf magnified and foreshortened. The leaves do this in order to avoid growing downwards, where the position of the bough and bud would, if the leaves regularly kept their places, involve downward growth. The leaves always rise up on each side from beneath, and form a flattened group, more or less distinctly in proportion to the horizontality of the bough, and the contiguity of foliage below and above. I shall not trouble myself to illustrate this law, as you have only to gather a few tree-sprays to see its effect. But you must note the resulting characters oneveryleaf; namely, that not one leaf in a thousand grows without a fixed turn in its stalk; warping and varying the whole of the curve on the two edges, throughout its length, and thus producing the loveliest conditions of its form. We shall presently trace the law of resilience farther on a larger scale: meanwhile, in summing the results of our inquiry thus far, let us remember that every one of these laws is observed with varying accuracy and gentle equity, according not only to the strength and fellowship of foliage on the spray itself, but according to the place and circumstances of its growth.
§ 15. For the leaves, as we shall see immediately, are the feeders of the plant. Their own orderly habits of succession must not interfere with their main business of finding food. Where the sun and air are, the leaf must go, whether it be out of order or not. So, therefore, in any group, the first consideration with the young leaves is much like that of young bees, how to keep out of each other’s way, that every one may at once leave its neighbors as much free-air pasture as possible, and obtain a relative freedom for itself. This would be a quite simple matter,and produce other simply balanced forms, if each branch, with open air all round it, had nothing to think of but reconcilement of interests among its own leaves. But every branch has others to meet or to cross, sharing with them, in various advantage, what shade, or sun, or rain is to be had. Hence every single leaf-cluster presents the general aspect of a little family, entirely at unity among themselves, but obliged to get their living by various shifts, concessions, and infringements of the family rules, in order not to invade the privileges of other people in their neighborhood.
§ 16. And in the arrangement of these concessions there is an exquisite sensibility among the leaves. They do not grow each to his own liking, till they run against one another, and then turn back sulkily; but by a watchful instinct, far apart, they anticipate their companions’ courses, as ships at sea, and in every new unfolding of their edged tissue, guide themselves by the sense of each other’s remote presence, and by a watchful penetration of leafy purpose in the far future. So that every shadow which one casts on the next, and every glint of sun which each reflects to the next, and every touch which in toss of storm each receives from the next, aid or arrest the development of their advancing form, and direct, as will be safest and best, the curve of every fold and the current of every vein.
§ 17. And this peculiar character exists in all the structures thus developed, that they are always visibly the result of a volition on the part of the leaf, meeting an external force or fate, to which it is never passively subjected. Upon it, as on a mineral in the course of formation, the great merciless influences of the universe, and the oppressive powers of minor things immediately near it, act continually. Heat and cold, gravity and the other attractions, windy pressure, or local and unhealthy restraint, must, in certain inevitable degrees, affect the whole of its life. But it islifewhich they affect;—a life of progress and will,—not a merely passive accumulation of substance. This may be seen by a single glance. The mineral,—suppose an agate in the course of formation—shows in every line nothing but a dead submission to surrounding force. Flowing, or congealing, its substance is here repelled, there attracted, unresistingly to its place, and its languid sinuosities follow the clefts of the rock that contains them, inservile deflexion and compulsory cohesion, impotently calculable, and cold. But the leaf, full of fears and affections, shrinks and seeks, as it obeys. Not thrust, but awed into its retiring; not dragged, but won to its advance; not bent aside, as by a bridle, into new courses of growth: but persuaded and converted through tender continuance of voluntary change.
§ 18. The mineral and it differing thus widely in separate being, they differ no less in modes of companionship. The mineral crystals group themselves neither in succession, nor in sympathy; but great and small recklessly strive for place, and deface or distort each other as they gather into opponent asperities. The confused crowd fills the rock cavity, hanging together in a glittering, yet sordid heap, in which nearly every crystal, owing to their vain contention, is imperfect, or impure. Here and there one, at the cost and in defiance of the rest, rises into unwarped shape or unstained clearness. But the order of the leaves is one of soft and subdued concession. Patiently each awaits its appointed time, accepts its prepared place, yields its required observance. Under every oppression of external accident, the group yet follows a law laid down in its own heart; and all the members of it, whether in sickness or health, in strength or languor, combine to carry out this first and last heart law; receiving, and seeming to desire for themselves and for each other, only life which they may communicate, and loveliness which they may reflect.