Although it is difficult to believe, there are fish living in the desert. Several important expeditions have gone to the Sahara to uncover the mystery of these fish which are sometimes found scores of meters down.

The most famous is the lungfish which lives in the larger African rivers. When these overflow their waters can spread out to desert regions to form small lakes or ponds. When the lake dries up the lungfish buries itself in wet mud where it can live for months on end, especially if it goes deep enough to find an underground layer of water.

Lungfish are among the most ancient bony fishes and are very like those which lived 200 million years ago, at the beginning of the Mesozoic Era.

Some plants entrust their pollen to the winds. Others use water as a carrier and still others simply pollinate themselves. However in most cases the vital task of pollination is carried out by insects.

To attract insects plants produce flowers that have been beautiful scents and colors. The shape of the flower’s corolla, the part with the petals, is designed to let pollination insects in but to keep out other unwelcome creatures.

Sometimes the pollinating mechanism inside a flower is amazingly complex. An example is the sage flower; when a bee is attracted by the scent or the nectar, it stands on the lowest petal to enter the flower. As it does so, the bee presses on a kind of lever which makes the flower’s stamens come down and touch the hairy back of the bee, covering it with pollen. The bee then enters another flower and the whole operation is repeated.

The sage is one of those plants that lets its stamens ripen before its pistil. So when the bee lands on a flower where the stamens and the anthers have withered away, there is a pistil waiting to pick up the pollen from the bee’s back to fertilize itself.

The pineapple plant produces large fruits and has a stalk that grows under the ground. This stalk pushes out a tuft of fleshy leaves which are up to meter long and are prickly at the edges. From the center of this crown of leaves there grows a stem which also has leaves growing on it. At the top of the stem there is a cluster-like flower of bluish blossoms.

When these flowers have bloomed the stem underneath them swells and produces the fruit which is sold fresh or in tins. Pineapple fruit can weigh up to 4 kilograms.

The top of the fruit has a tuft of leaves known as a crown. If the pineapple is placed in the ground in warm, moist conditions, this tuft of leaves will produce a new plant. This is one of the most common methods used to reproduce the fruit.

It was once fashionable to grow pineapple under glass in England, but this practice has now died out. Most pineapples are grown in Thailand. They are gathered unripe and allowed to ripen on the journey to their destination.

The truffle is a strange fungus that grows from 5 to 10 centimeters below the ground. It can only be located by the peculiar smell it gives out and the best way to find it is to use a pig or a dog which has been trained in truffle hunting.

The dog or pig is taken to the place on a lead. As soon as it smells a truffle the animal is released and runs to the spot. The pig digs the truffle up with its nose; the dog uses its paws. The animals are rewarded with some thing to eat.

Some truffles are as big as a clenched fist but others are much smaller. There are two main types of truffle: the black and the white. The white truffle is much more sought after for its pungent and penetrating taste. It is a pale, dirty yellow in color.