A seed is a fully developed fertilized ovule. A typical seed consists of a seed coat enclosing and protecting the embryo. The seed coat consists of two layers, the outer thick one, the testa and the inner membranous one, the tegmen. A scar known as the hilum is found on one part of the seed and is the point of attachment of the seed to the fruit. Just above the hilum is a minute pore, the micropyle. Water and air enter the seed through this opening during germination.