The flowering plants as general purveyors to the human race and their domestic animals
It is of course not only for food that humans use the many products of flowering plants. Substantial textbooks hundreds of pages long are available with the title ‘Economic Botany’ which deal with all aspects of the subject. It is very interesting to see, too, how little of each of these books needs to be devoted to non-flowering plants. We will try to carry out a survey of the chapters in an economic botany book and cite examples as we go through.
A. Materials for making things
Wood is probably the most important single economic product apart from food. Timbers such as oak, ash and beech are widely used. Teak and ebony are used where their hard, resistant properties are of especial value. Since all of these timbers are much more expensive than their counterparts in the non-flowering plants such as pine and cedar, they are often cut into very thin sheets and stuck on to cheaper wood. These very thin sheets are known as veneers and may be used to produce very beautiful effects.
In spite of the invention of many plastic substitutes, cork cut from the bark of cork oak trees is still very widely used for bottle stoppers, table mats and flooring material.
Although probably being gradually superseded by more modern synthetic materials, tree bark and other plant parts are used as sources of tanning and dyeing substances.
One of the most important of the fibres derived from plants is cotton. It is made from the almost pure cellulose hairs growing on the surface of the seeds of the cotton plant. Flax (for linen) and jute are obtained from the fibrous parts of those plants while sisal is derived from the leaves of the succulent Agave plant. Raffia comes from a species of palm tree and in addition there is a vast variety of plant leaves and stems that are used to make baskets of all kinds.
Rubber comes from a milky juice produced by Hevea trees.
Wood is also much used as a fuel. In hot climates it is in considerable demand as a heat source for cooking. In some countries such as India it is in short supply. If wood is heated in isolation from the oxygen of the air, it becomes charcoal which is another very useful fuel. In countries without sources of oil, such as Brazil, starch or sugar are fermented to produce alcohol which may be used as a substitute for petrol.
Gums and resins which are exuded by various trees are collected and used industrially. Lacquer is a natural varnish which is obtained from a species of Rhus, widely grown in China and Japan.
Many oils are extracted from the seeds of plants such as sunflower, corn and flax (linseed oil). In the case of olive oil, this is extracted from what is actually the fruit wall rather than the seed.
Important waxes are also obtained from plants to be used in making things like candles, varnishes, paints, and polishes. The most well-known is carnauba wax which comes from the leaves of the carnauba palm.
The history of perfumes dates back to very ancient times in Egypt, Rome, and Greece. Louis XIV’s court had a special perfume for each day of the year and the king himself supervised its preparation. A huge list of plants is involved in the manufacture of perfumes.
Medicinal plants also have a very long history. Details of their use are to be found in some of the earliest printed books, known as herbals.
D. Smoking and chewing materials
Some plant parts are used for pleasurable purposes. Tobacco and chewing gum are well known examples. The essential ingredient of chewing gum is a substance called chicle. This exudes from the bark of the sapodilla tree grown in central America and Florida. The bark is slashed diagonally, and the gum is collected in containers fixed to the tree. Betel nuts (from the betel-nut palm) and cola nuts (from the cola tree) are chewed by enormous numbers of people in the tropics and in China.
Tea, made from the leaves of Camellia sinensis, must be one of the most popular beverages throughout the world. In south America, a tea-like beverage called mate is obtained from the leaves of a species of holly. Coffee and cocoa are also drunk by large numbers of people in many nations. Alcoholic beverages all involve the use of various parts of flowering plants.
This is by far the largest category of useful materials produced by the flowering plants. Whereas many of the substances mentioned previously are not essential to the human race, food is absolutely vital. It may be obtained from all of the parts of plants: stems, roots, leaves, seeds, fruits, and compact groups of flowers. We shall deal with each of these in turn.
Perhaps rather surprisingly, the most common plant stem to yield food is the humble potato which is widely grown in the northern hemisphere. Although it develops underground it is in fact a stem; the ‘eyes’ are buds. Buds never form on roots. Another very important stem is that of the sugar cane which, when crushed, releases large quantities of so-called cane sugar. The Jerusalem artichoke is another example of an important food-bearing stem. Asparagus tips, a delicacy rather than a staple food, are the young tops of newly developed stems.
There are numerous examples of roots that are used for human food. Beets, carrots, parsnips, turnips, swedes, radishes, salsifies, sweet potatoes, and yams are widely grown as root crops. Some are also used as cattle feed. The variety of beet known as sugar beet yields beet sugar which is of the same type as cane sugar.
Leaves may be picked and used singly as in spinach or cut off in the form of large buds such as Brussels sprouts, cabbages, and lettuces. The principal parts of celery and rhubarb that are eaten are the leaf stalks, despite their resemblance to stems. Garlic, onions, shallots, leeks, and chives are compact masses of leaves.
Seeds are undoubtedly the most important plants foods. We will treat all the various cereal crops as seeds although, as explained earlier, each seed is enclosed in a fruit wall and is therefore a single-seeded fruit. The seeds of wheat, oats, barley, maize (corn), rice, millet and sorghum must keep untold millions of human beings alive.
Since the list of seeds is so enormous, only a selection of the remainder will be mentioned. There is a wide variety of peas, beans and peanuts which are all produced by the same plant family. Brazil nuts, cashew nuts, coconuts, walnuts, pecan nuts, almonds and chestnuts all make a considerable contribution to the human food supply.
Examples of fruits have already been mentioned in Chapter 6. Apples, pears, plums, apricots, cherries and peaches, grapes, bananas, dates may be added to the list and even then many would still be omitted.
G. Spices and flavourings
From earliest times human beings have sought to enhance the flavour of their food, particularly cooked food. Before the days of widespread refrigeration some of the substances used had the additional advantage of preserving the food. As with many of the categories in our list above the number of plants and their various parts that are used as spices and flavourings is enormous. At one time specific examples might only be used by one culture in one part of the world. However, now that numerous regions have become quite cosmopolitan it is possible to obtain all kinds of substances long distances from their original points of use. This is especially true of the northern hemisphere.
The evolution of the human race has depended heavily on the sources of food provided by the flowering plants. In perusing the list above (A to G) it is obvious that there is no aspect of human life that is not permeated by the use of plant materials of one kind or another. With the onset of civilization man has been able to improve upon the efforts of the plants so that productivity has been enormously increased.
In this account of the history of plant life on Earth we have traced the steps from the most primitive single-celled plants billions of years ago to the life-supporting flowering plants at the present day.