Groundnut do not have residual endosperm as it is completely consumed during embryo development, hence it is known as Exalbuminous seed. Castor retains a part of endosperm as it is not completely used up during embryo development, hence it is known as Albuminous seed.

Introduction:
Peanut, also known as groundnut, is a crop that belongs to the family Fabaceae. It is an important source of oil and protein and is widely cultivated in various parts of the world. In terms of its seed composition, peanut falls under the category of albuminous seeds.

Albuminous Seeds:
Albuminous seeds are characterized by the presence of endosperm, which serves as a storage tissue for nutrients. This endosperm is rich in proteins and other nutrients that are required for the growth and development of the embryo. Examples of albuminous seeds include legumes, such as peanuts, beans, and lentils.

Double Fertilization:
Double fertilization is a unique reproductive process that occurs in flowering plants. It involves the fusion of two male gametes with two female gametes. In the case of peanuts, double fertilization occurs as follows:

1. Pollination: Pollen grains from the male reproductive organ (anther) are transferred to the female reproductive organ (stigma) of the same flower or a different flower on the same plant.

2. Fertilization: One of the male gametes fuses with the egg cell to form the zygote, which develops into the embryo. The other male gamete fuses with the two polar nuclei present in the central cell to form the endosperm.

Post Fertilization: Structures and Events:
After fertilization, several structures and events take place in peanuts:

1. Embryo Development: The zygote undergoes divisions and differentiations to form the embryo. The embryo consists of a radicle (embryonic root), plumule (embryonic shoot), and cotyledons (seed leaves).

2. Endosperm Development: The fusion of the male gamete with the polar nuclei leads to the formation of the endosperm. The endosperm provides nutrients to the developing embryo during germination.

3. Seed Coat Formation: The integuments of the ovule develop into a tough seed coat, which protects the embryo and endosperm.

4. Maturation: As the embryo and endosperm develop, the seed undergoes maturation, during which it accumulates reserves of oil and protein in the endosperm.

5. Seed Dispersal: Once the seeds are mature, the peanut pod dries up and splits open, allowing the seeds to be dispersed. This can happen through various means, such as wind, water, or animal dispersal.

Conclusion:
In conclusion, peanuts fall under the category of albuminous seeds. During the process of double fertilization, the male gametes fuse with the egg cell and the polar nuclei, resulting in the formation of the embryo and endosperm, respectively. Post-fertilization, the embryo develops, the endosperm provides nutrients, and the seed undergoes maturation and dispersal.