During formation of seed, the outer integument gets converted to the outer, thick, hard seed coat called testa. The inner integument gets converted into an inner, thin, membranous seed coat called tegmen. The micropyle is retained in the seed. Water enters the seed from the micropyle and initiates germination. In most of the flowering plants, during the embryo formation, the nucellus is complete used up and there is no remnant of nucellus in the seed. In some plants such as castor and black pepper, small amount of nucellus may remain. It is called perisperm.