The Study of Plant Life, M. C. Stopes [fiction book recommendations .txt] 📗
- Author: M. C. Stopes
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Look at the others growing with the heather; there is the heath, which is so like it that almost the same description applies to it. Then there is the cranberry, which lies close to the ground, and is somewhat protected by the other plants, and has more delicate stems, and larger, flatter leaves, which are also rolled in at the edges. The bilberry has certainly larger leaves than these others, but notice in the early autumn how soon and readily they drop off, and leave the thick, green, ridged stem to do their work. The moorland grasses also have protected leaves; generally they are narrow and pointed, and the whole leaf rolls over, so protecting the side on which are the transpiring pores (see p. 102). All these plants have the appearance of protecting themselves from loss of water; how is it? It may seem strange when you remember that it is from our moorlands that so much of our water supply comes, and also that the moors are common in the north, where there is a large rainfall. All the same, the plants on a moor do actually require to preserve their water, as they suffer from “drought conditions.”
Stand on a high moor on a windy day, and you will soon feel how the force of the wind sweeps across it. Such a day is what laundresses call “fine drying weather,” and so do the plants. Then if you go on a bright sunny day in summer, you will soon feel how very hot the moorland can be, for there is no shade to be had anywhere, and the cool green glades of a wood offer a tempting change. The moorland plants suffer from this heat, and require to protect their transpiring pores from the glare, so that you will find all those that can do so, have rolled their leaves up tightly. Then notice the soil of the moors, how springy it is, and how black and “rich”; very often there are traces in it of the partly decomposed plants which form it. This is what is called a peaty soil, and may even be true peat. The decomposing plants in this soil give rise to an acid which is rather preservative, and at the same time it acts on the living plants and makes it difficult for them to draw in water by their root hairs. This kind of soil adds very greatly to the “drought conditions” of the moorland plants, for it makes it hard for them to use the water which surrounds them. All these things cause the moorland plants to be as sparing as possible of their water, and so they have the appearance of plants grown under dry conditions.
But why are there no trees on the moors, you may ask! It cannot be that they are on too high a level for trees to grow, for some even higher hills are clothed with them. The truth is that probably long ago there were trees on the moors, but men cut them down foolishly without having planted young ones between the old ones, which would have replaced them. When once all the trees are cut down on a hillside, it is very difficult for young ones to get a start again, because everything which makes it hard for ordinary small plants to grow hinders the young trees, and the worst of all these things is the strong wind, which can rush unchecked over the bare moor. A strong wind is more powerful than a young tree, and kills it.
The plantations of young trees which are to be found on the moorland have to be started on the sheltered side, and require much care and attention. You will notice that the trees which do grow there are those which are specially fitted for a hard life, such as the pine, larch, and birch.
Another feature of the moorland, and one which cannot long escape our notice if we walk about moors at all, is the number of patches of wet moss which shake and tremble beneath our feet, and may form great stretches of bog-land. Sometimes this is so soft that it gives way altogether, and one may be knee-deep in moss and water, where it looked firm enough to the eye. You will find this bog moss grows in a peculiar way, the fresh green branches growing up and up, while below lie the half dead older stems, which are partly preserved by the peaty acids. These layers of moss collect for many years, till very thick masses of peat-bog may be formed.
Among the bog-moss you will often find the sundew and butterwort (see pp. 114-15), which are two of our chief insect-eating plants. They love the boggy moorland, or a damp spot beside a little moorland stream.
There is a curious thing you may have the chance of seeing in a wet moor. If you find a stream dripping over a ledge some little distance on to the rocks below, you may see how thick and beautifully green are the patches of moss growing beneath its spray. If the stream has passed over much limestone (and is therefore carrying some in solution), you may see below the living moss much dead moss just covered with a thin coating of lime. Below this is more moss, which has been made quite hard with the lime, and is brittle and snaps if you try to bend it, while below this again is a hard, compact mass of stone which is made from the stony stems of the moss crushed together by the weight above them and filled in with more deposited lime. In some places great masses of rock are formed in this way. You have here, acted before your eyes, a piece of the history not only of the living and dying plants of to-day, but of the building of rocks, which may some day help in the building of mountains.
PLATE V.
WATER PLANTS GROWING PARTLY BELOW AND PARTLY ABOVE THE SURFACE OF THE WATER
PONDS
The water of a natural pond is crowded with plant-life. Do not go to one in a London park, which is cleaned out by the County Council at intervals, but to one which is left to itself, and you will find it full of interest.
Fig. 141. Water Buttercup, showing the much-divided water-leaves, and the simpler leaves rising into the air.
Some of the plants float freely in the water, as do the duckweeds, and others, such as the water-lilies, are rooted in the mud with their leaves floating on the surface, while yet others are rooted in the mud at the bottom and live almost entirely under water, like some of the potamogetons, or curly pond-weeds. The plants which are more or less attached to the muddy bottom, and have floating as well as submerged leaves, are perhaps among the most interesting, for they show two kinds of leaves. Look at a water buttercup, for example (fig. 141); on the surface of the water, or just above it, are the flowers and leaves, which are rather like the leaves of an ordinary buttercup. Follow the stem a little way down under the water, and you will see that the leaves are no longer simple, but are split up into many hair-like divisions, which sway about easily with the water’s movements. These two kinds of leaves are each suited to their position, as you will see if you think about them. The broad, undivided leaves on the top of the water expose their surface to the sunlight and do as much manufacturing of starch as possible, while the soft much-divided leaves below the surface are in keeping with their position, for they allow the current to pass between their fine divisions instead of pushing them up or tearing them, as it must do if they had broad, flat surfaces, which would be overpowered by the strength of the current.
Compare these leaves with those of the water-lily. In the lily you find no divided leaves, but they all rise to the surface and float there, spreading their expanded blades on the water. Notice what very long leaf-stalks they have, sometimes eight or ten feet in length. Think how absurd the plant would look on dry land, with its short stem and its huge leaf-stalks, though they are so well suited for floating in the deep water. In the air the long, soft stalks would flop about on the ground, as they need some support, but this they get in the water, which buoys them up and saves them from expending too much material in the formation of strengthening tissue.
Even those plants which, like the water marestail, can stand up by themselves some way out of the water, yet have softer stems than most land-plants, and far fewer well-developed “water-pipe” cells, because they are so surrounded by water that they can get it easily. Both these plants and the water-lilies, as well as many others, store air rather than water in their stems, and often the spaces in the meshes of the stem-tissue are filled with air, which acts both as an air reservoir and a buoy to float the leaves. We find all through the plant-world that the structure of a plant depends very much on the kind of conditions under which it is living, and in the case of those growing in the water, it is quite clear how the soft, air-filled stems are one result of their mode of life, and are well adapted to it.
Fig. 142. Duckweed, with simple leaves, and long roots hanging in the water.
In the ponds you will often find that the duckweed grows in large masses on the surface. Each plant seems to consist of but one leaf and a slender root about an inch long, hanging freely in the water. Sometimes two or more of the leaves are attached and form a little cluster, but it is exceedingly rare to find the duckweed in flower. Simple as it is, almost suggesting the algæ rather than the flowering plants by its general appearance, yet the duckweed is really a flowering plant. It is, in fact, one of the very tiniest of flowering plants which are known.
Floating with the duckweed are frequently many fine, thread-like algæ, sometimes quite free, and sometimes attached to stems or rocks. They are very delicate, unprotected plants, their whole body consisting of simple rows of cells. Notice how their feathery tufts cling together in a close mass when they are taken out of the water; they require its support and protection to enable them to live.
Fig. 143. Creeping rhizome of the Bulrush, which pushes out towards the middle of the pond.
There are many plants growing round the borders of the pond, half in and half out of the water, such as the reeds and sedges, irises and the tall marsh buttercups. Watch how these plants
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