The shell covering a seed is sometimes called a hull.
Seed coat.
the valence shell
germination
linseed.
Burr
seed leaves
To effectively shell sunflower seeds, first crack the shell with your teeth or a nutcracker. Then, use your fingers to remove the seed from the shell. Repeat the process for each seed.
gladius
Aril, testa, hull
An egg
Orbital x ray
It protects it's seed with the outer shell covering.