Brain rather than brawn is the cause of man's supremacy in this world. Of all the beings that inhabit the earth he knows best how to use for his own advantage all things that exist. His progress from savagery to civilization is marked by his growing power to domesticate animals and plants. Very early in his history man learned the value to himself of the seeds of the cereals. He discovered that they may be kept a long time without injury; that they contain a great amount of nutrition for their bulk; that they are easily prepared for food; that, when planted, they give largest return. Thus, we see, the advantages the plant mother had developed for her young, man has turned to his own use. That the food put up for the young plant is so protected and constituted as to endure unhurt for a long time gives the cereal grains their keeping quality. That it is concentrated and well packed renders it convenient for man to transport. That the "box" is easily separated from the "lunch" makes the preparation of food by crushing and sifting an easy matter for man. That every mother plant, to insure the continuation of the species, develops many seeds, so that in the great struggle for existence at least some shall survive, makes the cereals profitable for man to plant, and harvest the increase. Think once, how few ears of corn it requires to plant an acre. [Illustration: _Fig. 279. Section of kernel of corn, showing the embryo, and the food supply at one side of it (at the right)._] Because of all these things there has grown up between domestic plants and man a partnership. Man relieves the plant of the responsibility of scattering its seeds, and in return takes for himself that proportion of the seeds which would have died in the struggle for existence had the plant remained uncultivated. This partnership is fair to both parties. Different plants store food materials in different proportions in their seeds; the most important of these food substances are starch, oil, protein, and mineral matter. All of these materials are necessary to man as food. In the cereals the seeds contain a large proportion of starch, but in the nuts, like the butternuts and walnuts, there is a predominance of oil. Let us for a moment examine a kernel of corn and a kernel of wheat and see how the food is arranged. Fig. 279 is a kernel of corn cut in two lengthwise; at the lower left-hand corner are the root parts and leaf parts of the young plant (the embryo); above the embryo is the loose starch material. Now we have the baby corn plant lying at one side, and its food packed about it. However, this food is in the form of starch, and must be changed to sugar before the young plant can partake of it and grow. There lies a connecting part between the germ and its food, the scutellum. This is so constituted that when soaked with water it ferments the starch and changes it to sugar for the young plant's use.