Its the surface
Embryo & endosperm
Aril .
The seed coat is hard protective covering of the seed, developed from the ovule integuments. On maturity it becomes impervious to water hence does not allow water to come out or enter inside. Thus it protects the seed from injury and drying out.
Seed coat or testa.
Gymnosperms
Angiosperm
It is called a seed coat.
'Aril' is the scientific name for seed covering
Aril .
# # # # # #
If you mean the seed covering its called the Testa
Some seeds have an outer covering which makes it hard for insects and animals to get into. Sunflower seeds have a hard outer shell to protect itself from predators.
The seed coat is hard protective covering of the seed, developed from the ovule integuments. On maturity it becomes impervious to water hence does not allow water to come out or enter inside. Thus it protects the seed from injury and drying out.
For the sunflower (Helianthus annuus), the seed is a multilayered future plant that is enjoyed as a food source by many. What you see, when you have a sunflower seed, is the hard shell. It can be all black or striped. Break that open and you have the actual seed. The outer most covering on the seed, usually you don't notice it, is call the integumentary or seed coat.
It protects it's seed with the outer shell covering.
Seed coat or testa.
Hull
The shell covering a seed is sometimes called a hull.