Nuts

Botanically speaking, a nut is a dry fruit containing a single seed and having a hard, woody outer coat. Hazelnuts and sweet chestnuts are true nuts, and so are cashews and macadamia nuts, but in fact most of the other “nuts” that we buy in the shops are not nuts at all. They are mostly the inner parts of other kinds of fruits.

Walnuts, pecans and almonds, for example, are the equivalents of peach or plum stones, and until they fall from the trees they are enclosed in tough, leathery cases that correspond to the flesh of the peach or plum. Even the hard shelled coconuts are also the inner parts of the fruit, although here the outer part is thick and fibrous – it is used for coconut matting. Brazil nuts are actually hard shelled seeds that are obtained from ball shaped woody fruits.

Ground nuts or peanuts are the seeds of a leguminous plant, carried in pods. In all these examples, the parts that we actually eat are the seeds or kernels- the embryonic next generation of plants and their food reserves.

Unusual Adaptation

Flowering plants have evolved in many directions, becoming adapted to a wide range of habitats and acquiring many life styles. Plants growing on high mountains or on the northern tundra usually form mats or cushions close to the ground to escape the violent winds. The dwarf willow Salix herbacea, for example is a true willow, but it has underground stems and its aerial branches are rarely more than 3cm above the ground. The leaves and flowers of many mountain plants are darker than those of their low land relatives; dark colours absorb heat more efficiently in the cold climate.

Many plants manage to live in deserts despite the scarcity of water. Some of them are quick growing annuals that complete their life cycles in a short time and are not affected by the drought, but the typical desert plants store water through the dry season. Waxy or hairy coatings, and breathing pores sunk in deep grooves ensure that evaporation is cut to minimum. Many of the plants have very small leaves or none at all, although some species sprout leaves when the rains come and then drop them for the dry season.

Cacti nearly all grow in the American deserts and can survive prolonged drought. They have no proper leaves and their ribbed grooves store all their food. Wide spreading roots catch nearly all the rain that falls in the wet season and the stems swell up as they take up water. The stems shrink as they use up water in the dry season, and the grooves become deeper. The breathing pores in the grooves thus become better protected from the dry air. Spines protect the cacti from grazing animals seeking moisture.

Mosses, Ferns and Conifers

Mosses

Mosses and the closely related liverworts carry spores in stalked capsules. The capsules form only after the union of male and female sex cells. As in ferns the cells need moist condition so mosses flourish mainly in damp environment.

Ferns

Ferns generally carry their spores in little capsules under the leaves. The related horsetails carry their in fleshy cones at the tips of the stems. Although the reproductive process needs water, mature ferns can survive in dry places.

Conifers

Conifers bear sees on the scales of their cones. The cones are small and soft at first, but swell and become woody after pollination. When the seeds are ripe the cones either open slightly or fall to pieces to release them. Conifers are the best known of the cone bearing plants, known as gymnosperms.

The Plants

With something in the region of 300000 different kinds or species, plants make up one of the two great kingdoms of the living world. The chlorophyll they contain is responsible for the essentially green nature of the planet. Unlike animals, plants can manufacture their own food from simple inorganic materials mainly water and the carbon dioxide gas in the air, they are thus the primary producers of food and all terrestrial animal life depends on them, either directly or indirectly, for food.
Most animals stop growing when they reach maturity and each species has a fixed shape. But plants go on growing throughout their lives and although the leaves and flowers of a particular species generally have a fixed shape, the overall shape and size of the plant can vary a good deal according to its situation.

Leaving aside the flowers or other reproductive organs, a typical plant has three main regions – root, stem and leaf. The root anchors the plant and absorbs water and dissolved minerals from the soil by means of osmosis. Growth takes place by elongation of the cells just behind the tip and this forces the root down. Delicate root hairs just behind the growing regions absorb the water and pass it to tubes in the centre of the root.
The stem which may be soft or woody carries water and dissolved minerals from the roots to the leaves through a ring of tubes. Another set of tubes carries manufactured food down from the leaves and distribute it around the plant. The stem also arranges the leaves in the most efficient way for catching sunlight and in flowering plants, displays the flowers in the best position for achieving pollination. The leaves are the plant’s food factories. They are usually flat and have a number of veins. Continues with the tubes in the stems, the veins carry water to the leaf tissues for photosynthesis and also carry away the manufactured food. The undersides of the leaves have thousands of microscopic breathing pores that allow carbon dioxide in and oxygen out. They also release a lot of water vapor by evapo-transpiration.

Truffles, Gills and Pores, Lichens

Truffles

Truffles are subterranean fungi with solid, globular fruiting bodies. They grow mainly in broad leaved woods. The perigord truffle of southern France is a much prized and very expensive delicacy. The traditional way of finding truffles is to train pigs or dogs to sniff them out. Most attempts at cultivating truffles commercially have failed.

Gills and Pores

The typical mushroom gets its food from decaying matter in the ground. Its fruiting body is spherical when it first bursts through the soil, but it quickly expands to form a cap and stalk. The latter, often called the stipe, may have a ring showing where the rim of the cap was originally attached and there may be a cup or volva, at the base. Under the cap, most species bear numerous fragile gills arranged like spokes in a wheel. The gill surfaces release millions of spores, the equivalent of seeds in flowering plants. Other mushrooms looks more like sponges, scattering their seeds from thousands of minute pores.

Lichens

Lichens are among the hardiest of all organisms, growing in some of the hottest and coldest places. They clothe much of the arctic tundra. Each of the many species is actually a combination of a fungus and an alga. The alga can exist along, but the fungus cannot, so lichens are regarded as special kinds of fungi that rely on algae to provide much of their food.

The Fungi

The fungi were once regarded as simple plants, but their chemical makeup is very different from that of plants and they are now placed in a separate kingdom. A fungus consists essentially of a mass of slender threads, called hyphae, which absorb food from other living or dead organisms. The familiar mushrooms and toadstools are the reproductive stages of the fungi and are often called fruiting bodies. They are composed of tightly compacted hyphae and their role is to produce and scatter the dust like spores. If a spore reaches a place with enough food and moisture for survival, it will grow sending out a hypha. The name mushroom was originally used for just one or two species of fungi with edible fruiting bodies, all the other fungi with umbrella shaped fruiting bodies being called toadstools. However, the modern tendency is for all umbrellas shaped fruiting bodies, whether edible or not, to be called mushrooms. Although many species are edible and very tasty, they contain little food value.
Relatively few of the 100,000 or more known fungi are really poisonous but a handful is truly deadly. The death cam probably kills more people than any other fungus. Growing in broad leaved woodlands, this fungus has a greenish cap with white gills. One specimen is more than enough to kill a person, with a slow and painful death. Several related fungi can produce sever illness if eaten although they are not necessarily deadly. These include the fly agaric, common under birch and pine trees, the blusher common I both deciduous and coniferous woodland, and the verdigris fungus common in grass and woodlands.

Convergent Evolution

Convergent evolution is a common phenomenon, in which unrelated plants or animals come to resemble each other because they have adapted to similar ways of life. The similarity of some species of American cacti and certain desert living spurges in Africa is a good example. Seals and Penguins are apparently very different animals, but both are superbly adapted for swimming. Their limbs and general body shapes appear similar when observed in the water.
Few animals have a clear fossil record as the horse. The oldest known fossils of this family, from rocks some 55 million years old, are of a fox sized creature called Hyracotherium. Its teeth indicate that it ate leaves, and it probably lived in the forests. Fossils from successively younger rock layers show that the descendants of Hyracotheium gradually became larger and were represented by several distinct genera before producing the modern horse about two million years ago. Their toes were reduced to one on each foot and their teeth became larger and stronger to deal with tough grasses.