Caryopsis
In
botany, a
caryopsis is a type of
simple dry fruit — one that is
moncarpelate (formed from a single
carpel) and
indehiscent (not opening at maturity) and resembles an
achene, except that in a
caryopsis the
pericarp is fused with the thin
seed coat. The caryopsis is loosely called a
grain and is the fruit typical of the
Family Poaceae. Examples of plants that produce a caryopsis fruit are
wheat,
rice, and
corn. In these fruits, the "hulls" to be separated from many grains before processing are actually
flower bracts.
The term grain is also used in a more general sense as synonymous with cereal (as in cereal grains). Considering that the fruit wall and the seed are intimately fused into a single unit, and the caryopsis or grain is a dry fruit, it is not surprising that in general usage little concern is given to technically separating the terms "fruit" and "seed" in these plant structures.