After fertilization in plants, the ovule matures into the seed. In angiosperms, the ovule consists of two layers. The outer layer of two protective coverings called the integuments and the inner cells that form the nucellus. After fertilization, the ovule matures into the seed and the integuments from the outer seed coat of the seed. In dicots, the seed coat consists of two distinct coverings, a typically firm outer layer called the testa, and a generally thin, membranous inner coat called the tegmen. The nucellus may disappear completely or may exist as a thin layer called the perisperm in some species.