Chapter I: Adaptation

The study of plants appears to me to be one of the most delightful and instructive that can be taken up by young people. It has this advantage over many other pursuits that it can be carried on almost everywhere, for, even if the student’s lot is to live in a town, there are generally botanic gardens within reach, and visits paid in the country are made the more enjoyable when some special study can be carried on in the daily walks.

Then collections of dried leaves and flowers can be formed during the summer, and the arrangement and classification of these will provide pleasant winter occupation.

I fear that many young people are apt to consider botany a very dry study. They are naturally repelled by the long words and many technical terms used in describing plants.

It has long been my belief that the study of botany should be approached through the garden rather than the schoolroom, beginning with a country ramble which should be an object-lesson opening out endless paths for future study.

Our Heavenly Father has given us a beautiful world to live in, and, when our eyes have once been opened to observe what lies around us, nature becomes like an exquisite book of pictures, always revealing to us something new and wonderful as we turn over each fresh page.

It is suited to all ages; the baby child begins by gathering daisies and buttercups, while older children make wild-flower collections and perhaps work in their own little gardens watching the growth of seeds and slips.

The beauty of ferns and mosses is sure to lead to some painstaking study of those fascinating growths.

Later on the fact that all trees have flowers comes as a surprise to the unobservant, and thus, when rightly guided, young people can hardly fail to love a pursuit that promises such endless sources of interest.

In the chapters that will follow on the subject of plant life, I do not purpose to write for quite young children, as my hope is that older readers will explain what is written, and make it interesting to the little ones as they walk in gardens and fields, giving as it were object-lessons on buds, leaves, and flowers, and training young minds to search for themselves into the wonders that lie around them.

How much there is to learn about, even in the simplest things, some of the succeeding chapters will endeavour to show, for example:

How young plants grow out of seeds;

How those seeds are dispersed;

How much is folded up in a bud;

How flowers are formed;

How the bark splits off different trees.

Any one of these subjects would need very careful, patient observation truly to understand it.

I stand as it were only on the threshold of scientific research, and look with wonder at the work of such a student as Darwin, who gave twenty long years to observation of the common earth-worm before he wrote his deeply interesting book upon it. Again, we see Sir John Lubbock giving years of his life to the growing of seeds and their seed leaves, in order to learn exactly how plants begin their life, and two very thick volumes are required to contain the vast amount of information he has thus obtained.

These two examples will suffice to show that the minutest objects in nature are worthy of reverent attention, and if these chapters tend to awaken young people to a perception of this fact and act as a humble guide to new lines of thought, I shall feel that they have not been written in vain.

I fear it is impossible to explain the processes nature is carrying on in the plant-world without occasionally using scientific words, but, when I am obliged to do so I shall try to explain their meaning,[1], and when once we rightly understand an exact expression we soon begin to use it, because it is more convenient and often saves repeating a long sentence.

[1] See glossary at the end of the book.

I would ask my readers to try and obtain from their gardens and fields the various objects mentioned at the close of each chapter, and compare them with the plates, learning all about them as they read the letterpress.

This will, I feel sure, add much interest to the study, for having something to collect and examine tends to lighten mental work and enables us better to understand descriptive writing.

In this introductory chapter I will simply take a general view of vegetable growth and its adaptation to the situation in which it is found.

In many respects plants require the same conditions as animals, birds, and insects; they must have air, food, moisture and light in order to attain healthy growth, and although they differ from animals in being usually stationary, their life is carried on in a very similar way. Let us take a forest tree as a type.

It is anchored in the soil by its roots which are its feeding organs; through them it draws up various kinds of nourishment from the earth in which it stands.

The roots by several chemical processes render the elements they have taken up from the soil fit for the nourishment of the tree; they send it up through the stem and branches into the leaves, and these being the breathing organs have essential work to do in receiving from the air, and giving out again, certain gases which contribute largely to maintain the life and vigour of the tree. Thus it grows year by year, producing annually its flowers and seed, which is the end and aim of all plant life.

We can trace another analogy with animal life, in the necessity for pure sweet air, plants growing in a vitiated or smoke-laden atmosphere soon showing unmistakable signs of weakness. The stunted hedges and trees on the fringe of London always remind me of the poor, ill-grown children of the slums.

Besides the plant life which we see around us in the shape of trees, shrubs, and flowers, there are lower and perhaps still more wonderful forms of vegetable life affording endless fields of study.

Mosses, lichens, and fungi we are familiar with everywhere in the country, but below these again are such growths as the green stain[2] which makes the tree trunks in moist places as brilliant in colour as the leaves themselves. Looked at through a lens we see the colour arises from a growing plant of extremely simple form, little more in fact than a succession of cells, each living and increasing “after its kind.”

[2] _Protococcus._

Again, if we consider the process of fermentation, we find that when it is set up in a cask of wine its action is due to the growth of a minute vegetable that feeds upon the alcohol and sugar, and by robbing the wine of those two elements turns it into vinegar or acetic acid.

A somewhat similar growth causes the thick jelly-like substance we sometimes find in our inkglass when it has been allowed to remain too long without renewal; the minute germs floating in the air have found the ink suitable to them, and thus their mycelium[3] begins to form at the bottom of the glass, to the great discomfort of the writer.

[3] First form of fungoid growth.

The yeast with which our bread is fermented is another of these minute plants, and consists of oval cells which multiply with great rapidity when placed in a pan of flour, and kept in a warm atmosphere.

By the careful study of these lower forms of vegetable life, Pasteur, Koch, Frankland, and others have discovered and classified the germs or microbes,[4] as they are called, which give rise to various diseases. In books upon the subject, their different shapes are figured as they appear when immensely magnified, so that we can see that which will give rise to consumption, erysipelas, or cholera, and one reads with deep wonderment of all that science has ascertained of late years as to the presence in the air of these seeds of disease which are ever floating more or less around us. But for the restraining hand of God, it appears as if universal sickness and death would be our fate.

[4] Small living atoms.

Leaving these lower forms of growth, we may consider the three divisions into which plants are naturally classed as to their duration of life.

Annuals are those which grow and flower, and form their seeds in one year, within which their life-history is closed.

Biennials produce leaves only in the first year; by their aid they lay up stores of nutriment in the form of tuberous roots, on this food they can exist through the winter, produce flowers the following summer, perfect their seeds, and then die.

To this class we owe such useful plants as the carrot, parsnip, beetroot, and many others which afford us such nourishing vegetable diet.

Perennial plants live on for an indefinite number of years, flowering annually, in some cases dying down to the root in autumn, and producing fresh foliage the following year.

Water plants seldom have a fixed root, but remain floating, borne up and kept in position by the water, their roots being the means by which, in conjunction with the leaves, they derive nourishment from air and water. It is well worth while to observe the two forms of leaves in the water buttercup. Those on the surface are three-lobed, flat, and round, they absorb from the air such gases as the plant requires; while the leaves beneath the surface are divided into threads so as to offer no obstruction to the flow of water and enable the plant to collect needful food from the water. It can vary the form of its leaves according to its requirements, since in running streams it may often be found with the hair-like leaves only.

On the other hand, if its seeds are sown in moist earth, the seedlings will grow and develop those flat leaves only which are characteristic of land plants. This water buttercup, therefore, gives us a wonderful example of adaptation to surrounding influences.

Adaptation is remarkably shown in the Vallisneria, a grass-like water-plant, found in Southern Europe;[5] it grows in freshwater lakes, rooted in the mud, and yet its flowers need to be fertilised in the air. In order to effect this, the small male flowers detach themselves from their stems, and, rising through the water, float about upon its surface. The female flowers are borne on a stalk, spirally twisted, so that it can uncoil and allow the flower to reach the top of the water whether it be deep or shallow. There the two kinds of flowers meet, the seeds are formed and the stem coils up again and brings the capsule below the surface, where it gradually matures.

[5] It can generally be met with at naturalists’ shops where aquaria are sold.

The water-lily can grow a long or short stem as the depth of the water may require to enable its leaves to lie flat upon the surface. I have gathered lily flowers in my lake with stems from four to five feet long, where the plant happened to be growing in deep water.

In such plants as the mare’s-tail (_Hippuris vulgaris_), we find the stem specially adapted to a submerged life. Growing out of mud at the bottom of a stream the plant upholds its slender stalks by two different methods. Inside the epidermis (or outer skin) a strand of rather tough tissue running through the centre gives flexible support, whilst the rest of the space is filled up with very large air cells, which give such buoyancy to the stems that even if they are three feet in length they are kept upright in the water, rising ten or twelve inches above the surface. It is a valuable as well as a curious plant, as it has the property of absorbing the gases emitted by stagnant water, and tends thus to purify the air.

The same power of adaptation is to be found in sea-weeds. Those growing on rocky shores having short fronds covered with fructification, while out at sea, ribbons of oar-weed may be found many yards in length, formed, like the gulf-weed, of tough texture to bear the friction of waves and storms.

If we were travelling in a Mexican desert, we should find those remarkable plants which can be so well studied in the cactus-house at Kew Gardens. Bearing in mind that for many months the plant must do without a drop of rain, or in fact without moisture of any kind, it has been necessary that the leaf-surface should be reduced to prevent loss of moisture by evaporation, and so spines take the place of leaves, and the stems are encased in a thick leathery skin, which protects the plant from the burning heat of the sun. Very little moisture escapes through this thick green epidermis; therefore when rain falls the plants receive and store up their liquid food, and live sparingly upon it during the long periods of drought, which last for three-quarters of the year. Some of these cacti, as we see them at Kew, are tall, straight-stemmed plants, others low-growing rounded masses, little spiny cushions, almost like vegetable hedgehogs.

In the arid prairies of Texas, advantage is taken of the watery stores of the cactus, for when other supplies fail, its fleshy stems are cut open, and horses and cows greedily devour the succulent food, which answers the purpose of drink, as well as affording nutritious fodder.

Our British spurge-plants have green leaves, a thin epidermis, and all the ordinary characters of the plants of a temperate region, but by comparing them with the spurges found in Madeira, we see how climate causes adaptation to differing conditions. One of these spurges growing in my greenhouse has a tall column-like stem, no leaves, and a thick leathery skin, which would enable it to bear a hot, dry climate. It thus mimics the giant cacti of Mexico.

We may trace another contrast in our common groundsel and the large succulent groundsels of the Cape and the Canary Isles, with their thick fleshy leaves, the difference in form and texture being simply an expression of the wonderful modification due to climate.

The lovely tribe of orchids make the same provision for long periods of drought. Many of the species live in countries where the rainy season lasts about six months, and is succeeded by as many months of dryness and heat.

The air-plants we obtain from these countries have large pseudo-bulbs, that is, the stems are enlarged so as to be storehouses of nutriment upon which the plant exists, and by means of which it brings out the gorgeous flowers which make Brazilian forests such fairylands of beauty; every tree-branch being laden with parasitic orchids, their lovely blossoms lasting month after month without the aid of rain or dew, because Nature has provided each plant with its special store of food, and has thus adapted it to the position it is created to adorn.

Another of these perching-plants is _Tillandsia Usneoides_, known in Florida as Spanish moss, and often called “old man’s beard.” It hangs from the tree-branches in tufts, like grey hair, and grows in such profusion that it is collected and used for stuffing cushions. This curious plant has no roots, but simply hangs from the branches, and lives like the orchids by absorbing water from the moist air in the humid forests where it is found.

The absorption by the long, hanging, grey roots of the orchids in one case, and by the finely-divided leaves and stems in the other, are both instances of the wonderful way in which Nature “adapts” the parts of a plant to its requirements.

It often happens that seeds, blown hither and thither by the wind, chance to fall upon places which are quite unsuitable to their mode of growth; then we have an opportunity of seeing how their power of adaptation enables them to triumph over almost insuperable difficulties.

I have observed a tiny plant of groundsel growing out of a chink in a wall where there was scarcely any soil from which it could derive nourishment, contriving to live on, however, and make the best of its hard lot. Its stem, which should have been a foot high, could only attain about two inches, and instead of dozens of leaves it had but four, and yet it survived and even produced two small flowers, thus touchingly displaying its power of adaptation.

Another more remarkable instance which occurs to me was that of a seedling Scotch fir, which had rooted itself in a lump of house-leek on the top of a garden wall. For eight years the young tree managed to live and grow, until it became a symmetrical well-branched fir-tree, almost twelve inches high. By a supreme effort it produced a crop of miniature cones, and soon after it died from drought and starvation, the wonder being that it could have lived so long upon the modicum of food the barren wall supplied, besides having to endure at times periods of scorching heat as well as drought. The chief interest in this example is centred in the fact that as soon as fruit-bearing has been attained, then, and not till then, the little tree died, showing how persistently under all hindrances and difficulties a plant will endeavour to carry out the purpose of its creation.

We have seen in these instances some striking examples of the way in which plant-life is adapted to its surroundings. Our examples have been such as are easy of attainment, and such as we can verify with our own eyes; but even more wonderful are the adaptations hidden away in the recesses of the plant, and as we progress in our study these arrangements of cells and tissues will be revealed to us. In order however to see them, and to understand their true significance, we must proceed step by step to study the parts of an ordinary plant; because it is only by first mastering all we can of one part of a plant, and then comparing that part with other plants, that we can hope to gain real knowledge. Accordingly in our next chapter we shall take the root as our starting-point, and ascertain its functions and uses, and the part it has to play in the economy of the plant.

Specimens to be obtained:—Green stain on treebark (_Protococcus_); yeast; annual, biennial, and perennial plants; water buttercup leaves; vallisneria; water-lily stems; mare’s-tail plant; cacti; spurge; orchids; tillandsia; plants growing in wall crevices.

CHAPTER II

_ROOTS_

“While thus through all the stages thou hast push’d
Of treeship—first a seedling, hid in grass;
Then twig; then sapling; and, as century roll’d
Slow after century, a giant bulk
Of girth enormous, with moss-cushion’d root
Upheaved above the soil.”

+Cowper.+