SEED AND FRUIT

respectively, the characteristic reproductive body of both angiosperms (flowering plants) and gymnosperms (conifers, cycads, and ginkgos) and the ovary that encloses it. Essentially, a seed consists of a miniature, undeveloped plant (the embryo), which, alone or in the company of stored food for its early development after germination, is surrounded by a protective coat (the testa). Frequently small in size and making negligible demands upon their environment, seeds are eminently suited to perform a wide variety of functions the relationships of which are not always obvious: multiplication, perennation (surviving seasons of stress such as winter), dormancy (a state of arrested development), and dispersal. Pollination and the seed habit are considered the most important factors responsible for the overwhelming evolutionary success of the flowering plants, which number more than 300,000 species. The superiority of dispersal by means of seeds over the more primitive method involving single-celled spores, lies mainly in two factors: the stored reserve of nutrient material that gives the new generation an excellent growing start and the seed's multicellular structure, which provides ample opportunity for the development of adaptations for dispersal, such as plumes for wind dispersal, barbs, and others. Economically, seeds and the fruits that contain them are important primarily because they are sources of a variety of foods; for example, the cereal grains, such as wheat, rice, and maize; the seeds of beans, peas, peanuts, soybeans, almonds, sunflowers, hazelnuts, walnuts, pecans, and Brazil nuts; the fruits of date palm, olive, banana, avocado, apple, and orange. Many fruits, especially those in the citrus familylimes, lemons, oranges, grapefruitsare rich in vitamin C (ascorbic acid); unpolished cereal grains in vitamin B1 (thiamine); and wheat germ in vitamin E. Other useful products provided by seeds and fruits are abundant. Oils for cooking, margarine production, painting, and lubrication are available from the seeds of flax, rape, cotton, soybean, poppy, castor bean, coconut, sesame, safflower, sunflower, the cereal grains of maize, and the fruits of olive and oil palm. Essential oils are obtained from such sources as juniper berries, used in gin manufacture. Waxes such as those from bayberries (wax myrtles) and vegetable ivory from the hard fruits of a South American palm species (Phytelephas macrocarpa) are important products. Stimulants are obtained from such sources as the seeds of coffee, kola, guarana, and cocoa; and drugs, such as morphine, come from opium-poppy fruits. Spicesfrom mustard and nutmeg seeds; from the aril (mace) covering the nutmeg seed; from fruits of anise, cumins, caraway, dill, vanilla, black pepper, red or chili pepper, allspice, and othersform a large group of economic products. Dyes (Persian berries, butternut brown, sap green) and ornaments (Job's tears from the grass Coix, used for curtains; Abrus, Adenanthera, and Rhynchosia seeds for necklaces; others for rosaries) are also provided by seeds and fruits. Additional reading Works treating the nature and function of seed and fruit include T.T. Kozlowski (ed.), Seed Biology, 3 vol. (1972); P.F. Wareing and I.D.J. Phillips, The Control of Growth and Differentiation in Plants, 2nd ed. (1978), written with a physiologist's appreciation for the experimental approach, admirably covering various aspects of dormancy; L. van der Pijl, Principles of Dispersal in Higher Plants, 3rd rev. and expanded ed. (1982), a highly original and most stimulating book displaying a thorough knowledge of both tropical and temperate-region biology; J. Derek Bewley and Michael Black, Seeds: Physiology of Development and Germination (1985); and A.M. Mayer and A. Poljakoff-Mayber, The Germination of Seeds, 4th ed. (1989), a very readable, responsible account presented in a well-organized, fairly concise manner. Bastiaan J.D. Meeuse The Editors of the Encyclopdia Britannica