The outermost covering of the seed is seed coat. The seed coat has two layers, the outer testa and inner tegmen. The seed coat is protective and protect the seed from desiccation, mechanical injury and extreme of temperatures. It also protects the seed from the attack of bacteria, fungi and insects. The seeds are attached to the pericarp by a stalk called the funiculus. When the mature seed is detached, the funiculus leaves a scar on the seed called hilum. Just below the hilum is a small pore called the micropyle. Water is absorbed through the micropyle during germination of seed. Within the seed coat is the embryo, consisting of an embryonal axis and two cotyledons; one on either side. The cotyledons are often fleshy and full of reserve food materials. At two end of the embryonal axis are present radicel which represent embryonal root and plumule which grows and develops into the shoot system.
In gram, pea and beans the cotyledons are thickened and fleshy. The cotyledons store food materials for the growth of the embryo during the germination of seeds. Such seeds are called non endospermic seeds. In some seeds such as castor the endosperm form as a result of double fertilization, is a food storing tissue and called endospermic seeds.
