My Science School

          A legend says the coffee plant first grew in Kaffa, a province in south Ethiopia, where it was discovered by a goatherd called Kaldi about the year 850. Kaldi’s goats were reported to have skipped and pranced in a strange manner after feeding on an evergreen plant. The goatherd, so the story goes, tried some of the berries himself and excitedly dashed to the nearest town to tell of his find, which was called coffee after the name of the province.

          Another theory is that the word coffee is probably derived from the Arabic qahwah. Certainly coffee was introduced info Europe from Arabia during the 16th and 17th Centuries. The first license to sell coffee in the United States was issued to Dorothy Jones of Boston in 1670. The coffee houses of this time became famous meeting places for discussion.

          As the drinking of coffee be­came more popular, its production spread to Java, Haiti, Dutch Guiana, Brazil, Cuba, Jamaica, Puerto Rico, Costa Rica, Vene­zuela, Mexico, Colombia, the Hawaiian Islands and, in this century, Africa.

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The manchineel tree is dangerous because its sap and fruit contain poison. Its other name is Hippomane, which comes from the Greek and means “causing horses to run mad”

      The tree is a member of the Euphorbiaceous family and grows in tropical America, producing a crop of acrid, bitter apple-like fruits which drop spontaneously and carpet the ground beneath it. The sap is white and highly caustic, so that a drop on the skin produces a burning sensation and raises a blister. It used to be believed by many that to sleep beneath the tree meant certain death. But the great 18th century naturalist Nicolas von jacquin “reposed under it for hours at a time without inconvenience”.

     The wood has often been used for furniture as it is beautifully patterened in brown and white. Before felling the tree by hand, workman light a fire round the trunk, so that the sap thickness and does not run down the handles of their axes.

Laurel and holly trees have developed special kinds of leaves to seal the water inside them during the winter months.

    Both trees are evergreen .Instead of dropping all their leaves in Autumn, They shed old ones and grow new ones throughout the year. In winter the soil is too cold for the trees to draw water from it through their roots. Normal leaves would continue to transpire and to give off moisture until the trees died of drought. But the special leaves of the holly and laurel hold the water .their waxy surface and leathery texture make certain that the water is contained safely within the green tissues.

    Some of the holly leaves have a further modification. On the lower branches which are within reach of browsing animals, each leaf has a series of sharp point along its edge. The higher leaves have only a single point.

            The green colour in grass-and in most other plants-comes from chloroplast within the cells, each of which contains four different colours or pigments. These are: chlorophyll a, which is the strongest and is blue-green; chlorophyll b. which is yellow green; xanthophylls, which are yellow; and carotene, which is orange and gives carrots their bright colour.

            Grass goes from light green in early spring to dark green and brown in summer and' autumn because the amount of each pig­ment changes, like the paint on a palette, to mix new colours.