Analysis:

Seed coat: The skin covering a seed, usually tough and protective, derived from the integument at the ovule stage.

Sunflower seeds belong to achenes. Peel off the hard shell of sunflower seeds. The seeds inside are seeds, and the hard shell is the peel, which tightly wraps the seeds but does not heal with the peel. The base of the seed is a little bit healed with the peel, which can be found by peeling off the peel. The film outside the seed is the pericarp.

Watermelon seeds are seeds, including peel (watermelon peel), seed kernel (watermelon kernel) and seed coat (watermelon shell). The pulp of watermelon is developed from the placenta of seeds in the fruit.

The pericarp of caryopsis is thin, leathery, non-cracking, containing a seed, and the pericarp and seed coat are closely healed and difficult to separate. Dianthus is very small, so it is easy to be mistaken for seeds, such as rice, corn and wheat.