IF you have ever visited the Alps in early spring, you will know well by sight the dainty little nodding bells of the alpine soldanella — twin flowers on one stalk, like fairy tocsins, which push their heads boldly through the ice of the névé, and form a border of blue blossoms on the edge of the snow-sheet. Most people, to be sure, visit the Alps in August; and they go too late. Autumn is the time when heather purples our bleak northern moors, but when the central mountain chain of Europe, so glorious in April, has become comparatively green and flowerless. If you wish to see what nature can do in the way of rock-gardens, however, you should go to Switzerland in early spring. It is then that blue gentians spread vast girdles of blossom over the alpine pastures; then that the green slopes on the mountain sides are yellowed by globe-flowers; then that the poet’s narcissus stars with its white petals and scents with its sweet perfume the rich meadows on the spurs of the lesser ranges. Higher up, sheets of creeping rock-plants, close clinging to the uneven surface, fall in great cataracts of pink and blue over the steep declivities. As the snow melts, upward, the flowers open in zones, one after another, upon the mountain sides, so that you can mark your ascent by the variations in the flora, and the different successive stages of development reached by the most persistent kinds at various levels.

  There is one adventurous little plant, however, among these competing kinds, which in its eagerness to make the most of the short alpine summer does not even wait, like its neighbours, for the melting of the snow, but, vastly daring, begins to grow under the surface of the ice-sheet, and melts a way up for itself by internal heat, like a vegetable furnace. It may fairly be called a slow-combustion stove, not figuratively, but literally. It burns itself up in order to melt the ice above it. This wonderful plant is the alpine soldanella, the hardiest and one of the prettiest of mountain flowers; it opens its fringed and pensile blue blossoms in the very midst of the snow, often showing its slender head above a thin layer of ice, where it fearlessly displays its two sister bells among the frozen sheet which still surrounds its stem in the most incredible fashion.

  So much every tourist to the Alps in May must have noticed for himself, for whenever he reaches the edge of the melting ice-sheet he can see the ice pierced by innumerable twin pairs of these dainty and seemingly delicate blossoms. Comparatively few observers, however, have proceeded to notice that the soldanella, fragile as it is, actually forces itself up through a solid coat of ice, not exactly by hewing its way, but by melting a path for itself in the crystal sheet above it. Yet such is really the case; it warms the ice as it goes. The buds begin to grow on the frozen soil before the ground is bare, under the hardened and compressed snow of the névé — which at its edge is always ice-like in texture. They then bore their way up by internal heat (like that of an animal) through the sheet that covers them; and they often expand their delicate blue or white blossoms, with the scalloped edges, in a cup-shaped hollow above, while a sheet of refrozen ice, through which they have warmed a tunnel or canal for themselves, still surrounds their stems and hides their roots and their flattened foliage. This is so strange a miracle of nature that it demands some explanation; the method by which the soldanella obtains its results is no less marvellous than the results themselves which it produces.

  The winter leaves of soldanella, which hibernate under the snow just as truly as the squirrel or the dormouse hibernates in its nest, are large, leathery, tough, and evergreen. They are, in fact, just living reservoirs of fuel (like the fat of the dormant bear), which the plant lays by during the heat of summer in order to burn it up again in spring for the use of its flowers. When I use this language, you will think at first I am speaking figuratively. But I am not; I mean it in just as literal a sense as when I say that the coal in the tender of a locomotive serves as fuel for the engine, or that the corn in the bin of a stable serves as fuel to heat the horse’s body. These leaves contain material laid by for burning; and it is by burning that material up at the proper period that the soldanella manages to melt its way out of the wintry ice-sheet, and so to steal a march upon competing species.

  The process requires explanation, I admit; let us try to understand it. Everybody knows, as a matter of common experience, that animals are warmer in winter than the air which surrounds them; warm-blooded animals, that is to say, which form the only class most people trouble about. Not everybody knows, however, that the same thing is more or less true of plants as well — that many plants have the power of evolving heat for themselves in considerable quantities. But this is actually true; indeed, all growing parts of a stem or young leaf-shoot must necessarily be slightly warmer than the air around them. For, when you come to think of it, whence do animals derive their heat? “From the oxidation of their food,” the small boy of the day, crammed full of knowledge, will tell you, glibly. And what do you mean by oxidation but very slow burning? You may take a load of hay, and set a match to it, and it will burn at once quickly, by combining with the oxygen of the air in the open; or you may, if you choose, give it to a pair of horses to eat instead, and then it will burn up slowly, by combining with the oxygen of the air in their bodies. Lungs, in fact, are mere devices for taking in fresh oxygen, which then combines with the food or fuel in the blood of the animal.

  A century ago, Count Rumford pointed out that you might burn your hay as you chose, either in a horse or in a steam-engine; and that in either case you produced alike heat and motion. What we call fuel is just carbon and hydrogen, separated from oxygen; and what we call burning or combustion is just the re-union of the oxygen with the other elements, accompanied by a giving-off of heat equivalent in amount to that originally required in order to separate them.

  Now, the foodstuffs of most animals are plants or parts of plants, especially seeds or grains, as well as the rich stores of starch or oil laid by in roots, bulbs, and tubers. These are all of them reservoirs of food or fuel, produced by the plant for its own future growth, and meant hereafter to sprout or germinate. All seeds, when they begin to quicken, unite with oxygen and evolve heat; and this heat is just the same in nature, whether it happen to be set free within or without an animal body. If you give an ox corn, he will oxidise it internally and warm his own body with it; but if you let it germinate, it will oxidise itself, and so produce a very small but slow fire, which warms both the corn and the space around it. Similarly, all growing shoots combine with oxygen, and, therefore, rise in temperature. In early spring, when the ground just teems with sprouting seeds and swelling buds, with growing bulbs or shooting tubers, the temperature of the soil is sensibly raised; and this very heat, evolved by germination, becomes itself in turn a cause of more germination; each seed and root and bulb and sucker helps to warm and start all the others. Spring largely depends upon the warmth thus produced. The earth, during this orgy of growth, is warmer by a good deal than the air about it; warmer even than it is in summer weather — indeed, were it not for the number of plants which thus start growing at once, growth would be almost impossible in very cold countries. Like roosting fowls, they warm one another.

  You think, however, the amount of heat that can be thus evolved must be very insignificant. By no means. Take an example in point. What do we mean by malting? We collect together a number of seeds or grains of barley, we wet them thoroughly, and allow them to begin germinating. Each grain individually gives out only a small amount of heat, it is true: but when many of them lie together, the total volume of heat produced is very great, and the amount would be even greater if it were not artificially checked at a certain stage: for the maltster does not wish his malt to be “over-heated.” Malt, then, is nothing more than sprouting barley; and the heat it begets in the process of malting shows us very clearly how much warmth exists in sprouting seeds, or in the growing portions of young plants, buds, shoots, and tubers.

  At the risk of seeming tedious in this preliminary explanation, I must also add that flower-buds and flower-stems which grow and open very rapidly must similarly use up oxygen in their growth, and therefore distinctly rise in temperature. In a very few large and conspicuous flowers, such as the big white calla lily, this rise in temperature during the flowering period can be measured even with an ordinary thermometer. No bud can open without giving out heat; and the amount of heat is sometimes considerable.

  And now, I hope, we are in a position to understand how soldanella acts, and why it does so. It is a plant which grows under peculiarly trying conditions. It has to eke out a livelihood in the mountain belt, just below the snow-line; and it is a low-growing type, which must flower early, or else it would soon be overshadowed by taller rivals. For growth is rapid in the Alps, once the snow has melted. Soldanella has thus to blossom, and to secure the aid of its insect fertilisers, at the precise moment when they emerge from their cocoons in the first warm days of the short alpine summer. If it waited later it would be overtopped and obscured in a very few days by the dense and rapid growth of waving grasses, and aspiring globe-flowers, and long-stalked, bulbous plants that crowd all around it. So the soldanella seizes its one chance in life at the earliest possible moment, and makes haste to pierce its way through the solid ice-sheet, while lazier rivals passively await its melting. That alone has secured its survival and success in the crowded world of the alpine pastures. For you must not forget that while to you and me the Alps are an unpeopled solitude, to the alpine plants they are a veritable London of competing life-types.

  The canny plant lays its plans deep, too, and begins well beforehand. It has made preparations. All the previous summer it has been spreading its round leaves to the mountain sun, and laying by material for next year’s flowering season. Leaves, you know, are the mouths and stomachs of plants; and the soldanella has a type of leaves admirably adapted to its peculiar purpose: expanded in the sunlight, they eat carbon and hydrogen the live-long summer, and turn the combined oxygen loose upon the air under the influence of the sun. By the time winter comes, they are thick and leathery, filled with fuel for the spring, and, of course, evergreen. They have also long stalks, which enable them during the summer to stretch up to the light; but in autumn they descend and flatten themselves against the soil, so as not to be crushed by the snows of winter. The first of my illustrations (No. 1) shows a group of these fat leaves, seen from above, and flattened against the ground in expectation of the snow-sheet.

  The material laid by in the thickened leaves consists of starches, protoplasm, and other rich foodstuffs. The snow falls, and the leaves, protected by their hard and leathery covering, remain unhurt by it. The food and fuel they have gathered is stored partly in the foliage and partly in the swollen underground root-stock. All winter through, the plant is thus hidden under a compact blanket of snow, which becomes gradually hard and ice-like by pressure. But as soon as the spring sun begins to melt the surface at the lower edge of the sheet, water trickles down through cracks in the ice, and sets the root-stock budding. It produces, in fact, the very same effect as the water which we pour upon malting barley in order to make it germinate. And the same result follows, though here more definitely, for the soldanella has collected its material deliberately as fuel, and uses it up on purpose to melt its passage. It absorbs oxygen from the air below the snow, combines it with the fuels in its own substance, evolves heat from their combination, and begins to send up its nodding flower-buds through the icy sheet that spreads above it.

  The warmth the plant obtains by this curious process of slow internal combustion it first employs to melt a little round hole in the ice for its arched flower-buds (No. 2). At the beginning, the hollow which is formed above each pair of buds is hemispherical or dome-shaped; the stem pushes its way up through a dome of air enclosed in the ice; and the water it liberates trickles down to the root, thus helping to supply moisture for further growth with its consequent heating. But by-and-by the stem lengthens, and the bud is raised to a considerable height by its continuous growth. Still, so slight is the total quantity of heat the poor little plant can evolve with all its efforts, that by the time the stem is an inch or two long, the lower part of the tunnel has curiously frozen over again, by the process which Tyndall called “regelation,” and whose importance in glacier action he so fully demonstrated. In this stage, then, the melted space is no longer a dome; it assumes the form of a little balloon or round bubble of air, surrounding the flower-bud. At the same time, the ice beneath, having frozen again, almost touches the stem, so that the bud seems to occupy a small, clear area of its own in the midst of the sheet, with ice above, below, and all around it (No. 3). You would say that growth under such circumstances, in almost icy-cold air, was impossible — but if you examine the ice-sheet at the edge of the névé, you will find it studded by hundreds of such bubbles, each enclosing an uninjured soldanella bud in its centre. The reason is that the heat from the flower keeps the enclosed air just above freezing-point; and so long as it is not actually frozen soldanella is indifferent to the cold of its surroundings.

  Gradually, in this way, the little buds manage to bore their way to the surface and to the sunshine on the outside of the ice-sheet. At last the stalk melts its path out, and a flower appears on the top, in the centre of a small cup-shaped or saucer-shaped depression (No. 4). The exquisite blue bells are thus seen blooming in profusion, apparently out of the ice itself, or as if stuck into it. Unless you looked close, and noticed that their stems came from the ground beneath, you might even imagine they were rooted in the crystal mass of the névé. The edge of the snow-field in early spring is often pierced and riddled by hundreds of such soldanella borings; others above are in process of formation; and if you cut a piece open you will see inside how each is produced, with its narrow tunnel below, its balloon in the centre, or later, its saucer-shaped depression on the surface. Moreover, if you look at the foliage on the bare ground beneath, you will find that, when the flowers open, the leaves are no longer thick and swollen. All the fuel they contained has by this time been burned up for warmth; all the formative material has been duly employed in making the buds or blossoms, with the stems that raised them; and nothing now remains but drained and flaccid skeletons from which every particle of living matter has been withdrawn and utilised. Later on new leaves are produced in turn from the root-stock, after the ice has melted; and these new leaves, raising themselves on their long stalks, and catching the sunlight, begin afresh to accumulate material for next year’s growth and next year’s burning.

  But why do the flowers want so much to reach the open air at all? Why should they not blossom contentedly under the enclosing ice-sheet? A glance at No. 6 will serve to explain the reason. Flowers, after all, are mere devices for the fertilisation of the fruit; it is the seeds and the next generation that the plant itself is mainly thinking about. The blossoms of soldanella are noticeable to us lordly human beings chiefly because they are so pretty; they have a delicate blue or violet corolla, exquisitely vandyked at the edge, and divided (on a closer view) into five more or less conspicuous lobes; so it is their colour and their daintiness that make us so much admire them. But to soldanella itself — which, after all, has to earn its livelihood with difficulty on a stern and rocky soil — this beauty that charms us is a mere matter of advertisement. The plant wants its blossoms to attract the early spring bees and honey-sucking flies, which carry pollen from head to head, and so fertilise its seeds for it. And fertilisation, to the practical-minded plant, is the whole root of the question. It cares no more for the beauty of its flowers in themselves than the British manufacturer of cocoa or soap cares for the gorgeous colours and striking designs he lavishes on his advertisements. “Use Jones’s Detergent” is the keynote of the poster. The object of an advertisement is to catch the eye and secure the money of customers; the object of the flowers, for all their beauty, is just equally to catch the eye and secure the visits of the fertilising insects.

  No. 5 shows how all this is managed. At the very same time that the soldanella raises its timid flowers, the bees and flies a little lower down the mountain sides are just escaping from their cocoons as full-fledged winged insects. It is for their sakes alone that the pensive blossoms tint themselves in blue or violet, for you will find throughout nature that blue is the true bee colour; and flowers that depend most for fertilisation on bees or their allies are almost always decked out in blue or purple. If you examine a soldanella closely, too, you will see that all its parts are exactly adapted to the shape and organs of its most frequent visitor, here represented in the act of rifling its honey. Its bell-shaped blossoms just fit the insect in size; its stamens shed pollen just where his hairy body is adapted to receive it; its sensitive stigma is so arranged that he rubs the golden grains off on the receptive surface of the next flower he visits. Then the little capsules swell, and the seeds ripen; and the happy soldanella, becoming a fertile mother of future generations, has fulfilled the main purpose of its stormy existence.

  Sometimes, however, the ice-sheet above is too thick to pierce; and then the bud, after making manful efforts to melt its way out to the open air, is forced to give up the attempt in despair, and unfold its petals within its icy cavern. In that case, of course, no insect can visit it; and such cloistered blossoms are therefore obliged to have recourse to the inferior expedient of self-fertilisation. I say inferior, because all higher plants strive as far as possible to produce seedlings which shall be the offspring of a distinct father and mother. The last illustration (No. 7) shows two flowers which have lengthened their stalk in vain to the furthest point for which they possess material, but have failed to melt a way out of the solid ice-sheet. They are therefore driven to curl round the tips of their stamens and fertilise themselves — a process which almost always produces inferior seeds and very weak seedlings. It is in order to prevent such disastrous results on a large scale, and to avoid the evils of constant “breeding in and in,” that soldanella has invented its curious device for pushing its way boldly through its native ice-sheet to the sky and the insects. It goes there, not to look beautiful for you and me, but to secure the aid of its established pollen-carriers.

 

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