The oldest known graves in those deltas contained seeds of wheat and barley. Wheat flour contains an optimum amount of gluten, a protein which is valuable not only as a food but for another property. It makes bread dough so sticky and elastic that bubbles of carbon dioxide gas, from fermentation of the yeast mixed with it, are trapped and held, causing the dough to expand and rise. When baked, the bread is porous and fluffy. Flours made from rye, barley and rice do not have that property and some wheat flour is usually added.
Wheat is the best of all grains for handling and storage.
The rounded oblong seeds flow like quicksilver and mingle so closely that a bushel of wheat will make more than a barrel of flour. And wheat keeps so well that it can be stored for years or shipped around the world. Being a plant of the grass family, wheat will grow where rainfall is scanty, or where it is abundant, if the spring is cool and moist and the summer is hot and dry. It does best on deep well-drained loam and clay soils. There are many races, varieties and hybrids grown from northern Canada and Russia to Argentina, Chile and New Zealand.