Читать книгу Enid Blyton's Nature Lessons - Enid blyton - Страница 7
ОглавлениеFALLING LEAVES
“Lo! in the middle of the wood,
The folded leaf is woo’d from out the bud
With winds upon the branch, and there
Grows green and broad, and takes no care,
Sun-steep’d at noon, and in the moon
Nightly dew-fed; and turning yellow
Falls, and floats adown the air.”
In spring-time, we eagerly watched the fat buds of the trees break into leaf, and grow strong and green in the warm sun. It was lovely to see them, for the trees had been bare and brown such a long time. All through the summer they waved in the wind and grew a darker green. Now it is autumn, and once again the leaves change colour. Soon they will be dead, but instead of putting on sombre, sad colouring, they flare up into brilliant reds and golds, oranges and crimsons, as if to say, “We’ll make the most of things whilst we can.”
And so it happens that autumn is the gayest, most brilliant time of the year. Lanes, woods, and hills are ablaze with colours that harmonise and melt into each other as if they were mixed on a painter’s palette. Everywhere the eye is caught by a bright splash of colour, and, if the sun is shining, the country seems almost on fire with golds and reds.
WHY LEAVES FALL
(1) Chestnut twig showing leaf-scars. (2) Ash twig showing leaf-scars. (Below) Diagram showing cork layer (a) formed between leaf stem (b) and twig (c). One bundle of vein-fibres (d) has snapped; one still remains.
Walk down the lane. See the vivid crimson dyeing the blackberry leaves. Look at the hazel’s pale gold dress. See the hawthorn putting on its lovely, many-coloured gown—green and yellow, red and brown, with its crimson haws gleaming here and there. In the woods, the oak will soon be waving leaves of russet brown, which, in the pale winter sun, will stand out here and there like copper against the sky. The beech tree will don its wonderful robe of burnished gold, and spread the woods with a rustling, brilliant carpet that gradually grows darker and darker as autumn wears on. The beech leaves are perhaps the most beautiful of all autumn leaves. They are not speckled or freckled with many colours, but turn to a pure and perfect orange-gold that shines in the sun as if it were made of fine beaten metal.
The horse-chestnut trees turn to a lovely mixture of yellows and reddish browns, and their big leaves fall with a plop on the ground, leaving the tree bare enough for you to see exactly how many “conkers” there are left. Pick up a chestnut leaf, and see how beautifully the greens, browns, and yellows merge into one another. Yellow is a very favourite autumn colour. The white poplar puts on a golden yellow dress, too, and the field maple is of such a brilliant yellow that, when the sun shines, it looks as if it were alight with fairy fire. The birch tree, standing so dainty and graceful, dresses herself in a frock made of little golden jewels, that shimmer and flutter in the breeze and go flying to the ground by the score, whenever the wind blows gustily.
The wild cherry is a most beautiful sight, for it loves red, and it will change its green leaves to pinks and reds and crimsons, as if it were trying all the reds in the paint-box! The hornbeam uses many colours—green and yellow, ruddy gold and rusty red—and makes itself as gay as if it were going to a party.
For a little while, the trees stand gay and bright, and the countryside is splashed with colours. Then, as the leaves begin to fall, the trees show their fine bodies—their dark trunks and graceful branches. The ash drops its leaves first, and the others follow—chestnut, beech, elm, birch, and hawthorn—all make a yellow, red, or brown pool around their feet, and the wind stirs and ripples it with a lovely rustling sound. The oak keeps its leaves for a long time, and the hazel clings to its pale golden leaves even to the middle of winter; but sooner or later they all fall, and the trees stand quiet in the wind, for, with the loss of their leaves, they have also lost their whispering voices.
Why Do the Leaves Change Colour?
The most important thing to notice about the leaves is their beauty. You all love colours, and here you will find some of Nature’s very loveliest ones. Collect all the brightest leaves you can find, bring them to school, and when the sun shines, hold them up so that the sunlight pours through the leaves; you will be delighted at the brilliant colours you see.
But you will want to know something else about autumn leaves besides their beauty. What makes them change colour? Why do they fall? They change colour, because the cooler weather and the shortening light act on the green colouring of the leaf in such a way that it is gradually destroyed and disappears. Other coloured substances are formed, and the leaf changes its hue. If red-coloured matter or pigment is formed, then the leaf will be red, as in the creeper that flares crimson over the walls of houses. If the pigment is yellow, the leaf gradually becomes yellow, as in the bright field maple. If there are many pigments, the leaf will be speckled and blotched, as are the leaves of some brambles.
Why Do They Fall?
And now, what makes the leaves fall in autumn? How is it that they cling so tightly to the tree all the spring and summer, and yet flutter to the ground when autumn winds puff and blow?
If you see a branch of a tree broken off by accident in the summer, you will have noticed that the leaves, though withered and brown, are still tightly clinging to the branch, and you will have to pull them off sharply, if you want to strip the branch. But in autumn, the leaves fall almost at a touch. The wind blows roughly, and down they come! Or a wet day comes and down they fly again, unable even to bear the extra weight of the moisture!
This is what happens. The time has come when the trees want to sleep. All the food that is in the leaves is taken into the tree and stored away. No leaves, save the specially strong ones of the evergreens, can stand the cold weather, for they are too thin-skinned; so the tree has no further use for them. If they stayed on, they would only wither, and use up space which is already wanted for next year’s buds. Also, if snow came, the leaves might carry the snow and break the tree branches with the weight, just as some evergreens crack when the snow bears too heavily on their strong branches.
“So,” says the tree, “we don’t want you any more. You have done your work, and breathed for us, made food for us, and given out water for us. Now you may put on bright dresses, fly in the wind, and come to rest.”
The tree has a clever plan for helping the leaves to fall. Just where the leaf-stalk joins the twig, a layer of cork begins to form. This layer separates the leaf-stalk from the branch or twig, and only the little thread-like strings that run down the veins of the leaf into the stalk remain to hold the leaf still on the tree. One by one these snap, and, when the last one breaks, the leaf falls.
If you pick a leaf in summer, you will leave a little round wound, a wet gash on the stem, for the tree is not ready to part with its leaves, and the thread-like vein-fibres have been torn away. But if you pick an autumn leaf and look at the place you plucked it from, you will find no wound, but a scar already dry and healed! Pick a horse-chestnut leaf and see the lovely horse-shoe scar left on the twig. Look at the base of the leaf-stalk and see the horse-shoe there too, exactly like the one on the twig. Then you can see how the vein-fibres once ran into the twig, and were gradually broken by the tree itself when the layer of cork grew between. If you look at the ash twigs, you will see their little leaf-scars quite plainly too.
The Leaf’s Last Work
The leaf has one more use before it disappears altogether. As it decays, it makes the ground rich, so that the soil every year has fresh goodness added to it. The leaves of some trees make the ground richer than others, and you will find many flowers growing below these trees in the spring-time.
Evergreens
Evergreens do not drop their leaves in autumn as other trees do. They drop them gradually all the year round, others taking their place, so that the trees seem always green. We are glad to have them in winter, though during the other seasons they look very dull and sombre, against the fresh greens or brilliant yellows and reds of the other trees.
Something to Do
If you want to brighten up your schoolroom in winter-time you can do it very easily. Pick some sprays of golden beech leaves from the woods (only just as many as you want, for remember you have no right to disfigure trees), and take them home. Put them flat under a carpet on which people tread a good deal, and let them stay there for two or three weeks. Don’t move them. Then take them out, bring them to school and put them in a tall vase. You will find that the lovely orange-brown leaves will remain on the branches all the winter through, and make the corners of your schoolroom bright and lovely. And when the “Book of Nature getteth short of leaves,” you will still have some graceful sprays to remind you of the time when the woods were brilliant with all the colours of the autumn.
QUESTIONS TO ANSWER AND THINGS TO DO
(1)
Describe a tree in its autumn dress. What happens when the wind blows?
(2)
How is it that the leaves fall at a touch in the autumn?
(3)
Do evergreens ever drop their leaves?
(4)
Put down the names of two trees that drop their leaves in autumn, and two trees that are evergreen.
(5)
Draw and colour a gay autumn leaf.
(6)
Find some bright sprays and bring them to school.
