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Medicinal plants - Реферат


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Medicinal plants

The plant kingdom is rich and varied. There are some 500,000 different species of plants. Plants have different "natural homes" (habitats). Cultivated plants from the garden differ greatly from the plants growing in the field or in the meadow. Some plants are familiar to you. You feast your eyes on modest bell-flowers, timid violets, bright poppies, luxuriant roses, fragrant lilac, long clusters of showy coloured flowers of hollyhock and evergreen leaves of ivy.

Don'tgather meadow and field flowers into bouquets. Some of them are rare species. Many plants produce poison that can kill or sicken people that come in contact with the plant. Touching poison ivy (a shrubby or climbing plant that has small, greenish berries and leaflets in groups of three) causes a severe, itching skin rash; eating certain holly berries (a shrub or a tree having evergreen leaves with pricky edges and bright-red berries) causes vomiting; chewing a stem of hemlock (a poisonous plant with featherlike leaves and flat clusters of small whitish flowers) can kill an adult.

The best rule for dealing with plants is: never eat or chew any wild plant.

But some of the chemical plants are used to produce medicines that ease human suffering and cure serious illnesses. Medical plants and some poisonous ones serve as a raw material for medicines.

A plant with a slender cluster of fragrant bell-shaped white flowers is called lily of the valley. It is a raw material for extracts to cure heart diseases. A bitter medical drug made from the dried juice of aloe (a tropical plant with thick, spiny-toothed leaves) is used to stimulate the digestive tract. The juice extracted from fresh leaves is used for applications on fester wounds and abscesses.

A North American shrub with yellow flowers that bloom in late autumn or winter is called witch hazel. A spicy-smeliing liquid made from the bark and leaves of this plant and rubbed on the skin relieves an open injury or wound pain. Early Native Americans were good at using various herbs and plants for medical purposes. The Hurons had a cure from scurvy (a disease caused by lack of fresh fruit and vegetables). They made a tonic from the bark and needles of an ever green tree that carried massive dozes of vitamin C. The Incas used a colourless substance from certain cinchona (a South American tree) barks to cure malaria. Bitter drugs or chemicals derived from quinine are used to treat malaria nowadays.

Over 200 years ago, doctors prepared medicines from the bark of willow trees. The bark contains a chemical that can ease or reduce fevers. The willow bark contains salicylate, an active ingredient of aspirin.

Plants grow in almost every part of the world. We see such plants as flowers, grass and trees nearly every day. Plants also grow on mountaintops, in the oceans, and in many desert and polar regions.

Without plants, there could be no life on the earth. People could not live without air or food, and thus could not live without plants. The oxygen is the air we breathe comes from plants. The food that we eat comes from plants or from animals that eat plant. Much of our clothing is made from the fibers of the cotton plant. But not only this. Many useful drugs come from plants. Some of there plants have been used as medicines for hundreds of years. More than 400 years ago, for example, some Indian tribes of South America used the bark of the cinchona tree to reduce fever. The dark is still used to make guinine, a drug used to treat malaria and other diseases. Another drug, called digitalis, is used in treating heart disease. It is made from the dried leaves of the purple foxglove plant. The roots of the Mexican yamare used in producing cortisone, a drug useful in treating arthritis and a number of other diseases.

The collection and use of medicinal plants began many thousand years ago.

Hippocrates, the father of medicine who lived in Greece wrote in his books about such drugs as hemlock , gentian and many others.

Today many drug plants are cultivated and many drug plants are collected from fields and woods.

Some drugs are made from fruits, leaves, flowers, roots, seeds of the plants.

It is very important to collect plants in proper time. Leaves are collected when they are fully developed. The time of the day is also important in the collection of drug plants.

Flowers are collected before the time of pollination. Fruits are collected when they are fully grown but unripe.

To dry plants correctly is also very important. If it is made carelessly the drug may be spoiled. Drug plants which have glicosides must be dried at a low temperature.

And now I want to tell you some words about mint and camomile.


Mint is the name of a large family of plants. There are about 3500 species of mint. Most mint plants have small, white, bluish or pinkish flowers. Their leaves are dotted with small glands that contain aromatic oils. The oil are released when the leaves are crushed.

Popular cooking mints include marjoram, rosemary and sage. Such mints as white horehound and peppermint add a cool, sharp flavor to candies. Mints also are used in some medicines and perfumes.


Camomile, is a group of small plants that are sometimes used in folk medicine. The name is often spelled chamomile. The most commonly cultivated camomile grows in the eastern and central regions of the United States, where it was brought from Europe. It is called common or corn, camomile, and sometimes the English, or Roman, camomile. The flowers look much like daisies. The flowers and leaves smell sweet, but taste bitter. They are sometimes applied as a poultice (warm, moist mass) to treat toothache, or made into a tonic.