Explain the structure and types of seeds.

(N/A) In angiosperms,the seed is the final product of sexual reproduction.
It is often described as a fertilised ovule. Seeds are formed inside fruits. $A$ seed typically consists of seed coat$(s)$,cotyledon$(s)$,and an embryo axis. The cotyledons of the embryo are simple structures,generally thick and swollen due to the storage of food reserves (as in legumes).
Mature seeds may be non-albuminous or albuminous.
$1$. Non-albuminous seeds: These seeds have no residual endosperm as it is completely consumed during embryo development (e.g.,pea,groundnut).
$2$. Albuminous seeds: These seeds retain a part of the endosperm as it is not completely used up during embryo development (e.g.,wheat,maize,barley,castor,sunflower).
Occasionally,in some seeds such as black pepper and beet,remnants of the nucellus are also persistent. This residual,persistent nucellus is known as the perisperm.