Cereals are members of the grass family (Poaceae or Gramineae) and produce dry one-seeded fruits (caryopsis) which are commonly called a kernel or grain. All cereals consist of a fruit coat (pericarp) surrounding the seed. The seed contains an embryo (germ) and an endosperm surrounded by a nucellar epidermis and a seed coat (testa). In addition, some cereals, such as rice, oats, and barley retain their husk during threshing, which must be removed to produce acceptable foods for humans. The bran consists of outer layers of the grain of cereals, removed during the process of milling and used as a source of dietary fiber. It generally comprises the fruit wall, seed wall, aleurone layer, and small amounts of the starchy endosperm and germ.