The nutritive perisperm tissue is encircled by the embryo along the seed margin. The radicle protrudes slightly, producing a visible bump in the circumference of the seed (called the "beak"). Surrounding the perisperm and embryo are three layers: the inner epiderm, the outer epiderm, and the pericarp. The inner epiderm is also called a tegmen. The outer epiderm is synonymous with testa. Together, the outer and inner epiderm make up the seed coat. In "Chenopodium" literature, the terms outer epiderm, testa, and seed coat are often used interchangeably.