What ingredient of Yumil-gwa, in a botanical context, implies that the shell is indehiscent?
Yumil-gwa:  Ingredients that are typically added can include: honey, cooking oil, cinnamon powder, nuts, ginger juice, jujube, and "cheongju" (rice wine). Nut (fruit):  In general usage, a wide variety of dried seeds are called nuts, but in a botanical context "nut" implies that the shell does not open to release the seed (indehiscent).
i don't know