The Study of Plant Life - M. C. Stopes (korean ebook reader TXT) 📗
- Author: M. C. Stopes
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In this the simplest family of all, we find more variety in the appearance of its members than in any of the others, so that it may seem to be rather difficult to recognise the plants which belong to it. Perhaps the easiest way of settling this, is to see if the plant fits into any of the other families, and if it never has flowers nor cones, neither fern spore-capsules nor the big spore-capsules of the moss family, then you are fairly safe in classing it with the simplest plants.
Very many of the plants of this family are found living in water, which is perhaps one of the reasons that they can afford to be so simple, because the water protects them from many of the dangers land-plants have to prepare against, such as wind, drought, or too much sunshine. This is the simplest family of real, undoubted plants; but there is one class still simpler, and that is the family of bacteria, about which you must have heard much, as many of them cause our diseases, though others do much valuable work for us. All the same, we will leave these little creatures alone, and content ourselves with the five great families of plants which we can see with our own eyes.
PLATE IV.
A LOW EDGE OVERGROWN WITH FOXGLOVES AND MANY OTHER WILD PLANTS
PLANTS IN THEIR HOMES CHAPTER XXVIII.
HEDGES AND DITCHES
We do not see plants growing under quite natural conditions in the hedges and ditches, because they are put there by man in the first instance, and are continually kept in order by him. All the same, the hedgerows, which are so common in England, deserve a little study. They are within the reach of every one, and there we may often find many wild plants growing sheltered by the actual hedge.
The principal plant is, naturally, the one which forms the hedge, and this is very commonly the hawthorn; but, growing under it, and over it, and on the banks on either side, there are many others which are generally quite self-planted and truly wild. Of the bigger ones, the white clematis or Travellers’ Joy is very common in the south of England, and grows climbing all over the hedge, and often covering it with its white flowers. We noticed this plant among those which are special climbers (p. 105), and we can often see very well on the hedges how it climbs over tree and shrub, and supports itself on them.
A smaller plant, of somewhat similar habit, is the goosefoot. This has long, weak stems, which grow up amidst the other vegetation and so support themselves, while its leaves are arranged in whorls round the stem, and are narrow and rough, and help to keep the plant from slipping down. Notice also its fruits, how rough they are, and how they cling to everything. They are beautifully adapted to catch on to every passer-by, whether man or animal, and so to get carried to a distance where the seeds may grow.
A character of the ordinary plants growing in the hedges is the tendency they often have to form very long, straggly stems, which are too fine and weak to support themselves, but which are quite strong enough to grow up through the hedge and bear leaves, as they are partly held up by the other vegetation. You may frequently find plants which are usually only a foot or so high, and able to support themselves very well, growing up through the hedge to a height of two or three feet, and having thin, limp stems with long spaces between the leaves (see fig. 136). These plants have some of the characters both of those grown in the dark and of climbing plants, because the thick-set hedge keeps off the light from the low-growing parts, so making them straggly, and at the same time gives them the support they need if they grow rapidly out into the light, and do not build strong stems. Very often you may find plants of the same species as those that grow so tall in the hedge, growing in the shorter turf away from it, and there only reaching their usual height.
Fig. 136. Two Toadflax plants growing near together: A, on the bank by a hedge; B, among the plants of the actual hedge.
This shows us not only that different species are specialised to grow under different conditions, but that even two individual plants of the same species may be growing within a few feet of each other, and yet have quite a different appearance owing to the influence of their immediate surroundings. There are many such cases to be seen in the hedgerows.
If the hedge runs from east to west, it will cast a shadow over the side lying to the north. Notice how different is the general appearance of the plants on the bleak side from that of those on the south. You may also find that some species which grow on the south side do not grow on the north at all, or only in far smaller numbers. It is quite worth while making out lists of all the plants you can find on one side and the other of the hedge if it is a big, well-established one, and comparing the numbers and condition of the two sets of plants.
Fig. 137. A, Dead Nettle which has grown up through the hedge. B, the same after being cut back with all the others. Side branches have begun to sprout now that it is well lighted and the top has been cut off.
As we noticed before, hedges are not entirely natural, and as man therefore forms a part of the plants’ environment, it is quite interesting to see how they respond to his influence. For example, we may study the effect of his trimming the hedge. In a hedge which had been left for some time to itself, the plants would have long, thin stems, bare at the base, where no leaves would develop, as they would be cut off from the light by all the other plants. Then comes the “hedger and ditcher,” and cuts them all back, leaving often only a few inches of nearly leafless stem. What is the result? Soon on these bare stumps leaves begin to sprout now that the light can get at them and the top is cut off, and many short side-branches come out, also bearing leaves, so that where before were only long, bare stems carrying the top tufts of leaves out to the light, we now have short, thickly clustered plants of bushy appearance (see fig. 137). Soon, however, the race for light begins again, and the plants grow taller in their attempt to overtop each other. Notice also how the hawthorn (or whatever woody plant it may be which makes the hedge) responds when its leafy shoots are cut away. Many hidden and sleeping buds in the brown woody stem now get their chance and wake to active life. It is this continual cutting back which makes the hedge so thick with many short branches.
Fig. 138. Bulrushes growing in a wet ditch.
In the ditches, which often run alongside of hedges, we find quite a different set of plants. The ditches are generally cut out to a lower level than the surrounding bank, and so they often contain water while the rest is dry. In such watery ditches the plants which you will find depend a good deal on the quantity of water in the ditch, and whether it is always there or not. If it is really a wet ditch, you may get many of the inhabitants of the lakes, or if it is a dry ditch where but little moisture collects, you will get only rushes and rank grass. An interesting kind of ditch to watch is one which is well supplied with water nearly all the year round, but may dry up during the height of summer. In such a position as this you are nearly sure to find many pond-dwellers, such as water-cress, duckweed, water parsnip, water buttercups, bulrushes, reeds, and many others, which will vary with the locality. These plants generally choose a spot where there is a permanent supply of water, but plants cannot foresee the unexpected draining of the ditch, or a summer drought, and they are sometimes left through these causes to grow on bare mud. When this happens, notice how they behave; those which were already rooted in the mud may continue to flourish for some time, while those which were floating may be able to root themselves and tide over a short danger. If the water is permanently drained off, however, they gradually have to give in; they seem to draw themselves together and the long, luxuriant branches die off, only the short shoots remaining, which are not so extravagant with water. The duckweeds, which you know very well as little floating green leaves, have long, thread-like roots hanging from them unattached to the soil. When the water goes, they first root themselves in the soil with these water-roots, but if the drought lasts long the roots die away and the plant hides in the mud, where it can remain for a long time waiting for the return of the water.
Fig. 139. Duckweed, with simple leaves and long roots hanging in the water.
In the ditches you will probably find a number of green, thread-like algæ; these may also remain on the mud for some time when they are dried up, and in their case some of the cells at such times get a specially thick coat, and remain living for long. Then, if the water returns, it is again the home of these algæ, which rapidly grow out from their protected cells.
So that you see, even if you had no plants but those in the hedges and ditches to study in their homes, yet you could manage to find many examples of living plants which are trying to fit themselves to their ever-changing surroundings. Those that cannot succeed must die away in that spot, and confine themselves to some other place where the struggle is not too hard for them. All the plants which we find anywhere living together are, therefore, those which are suited to the conditions in that place, and all such plants growing together in this way form what is called a “plant association.”
MOORLAND
Fig. 140. A moorland stream. Notice the low growth of all the plants.
The word “moorland” brings at once to the mind’s eye great stretches of land which the farmer has left practically untouched. It is not like a woodland, for the plants are all so short that they do not shut out the view; hence on the moors there is a sense of space, and one can see all around the hillsides and plateaux clothed, though their form is not hidden, by their covering of plants. Let us see what are the characters of the plants which grow so lowly, and yet so thickly on these expanses of uncultivated ground. Almost the first which rises to one’s mind is the heather, with its short, bent stem and many wiry branches. If
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