Caryopsis

Etymology:
– Term “caryopsis” from Greek words “karyon” and “-opsis”
– Coined by Achille Richard for dry, monospermic, indehiscent fruit in grasses
– Definition challenged by some botanists within the Gramineae family
– Diverse forms of caryopsis include achene-like, berry-like, and nut-like structures
– Types of caryopsis distinguished as modified and true caryopsis

References:
– Merriam Webster and Encyclopædia Britannica definitions
– Works by Louis-Claude Richard and Charles-François Brisseau de Mirbel
– Publications by Henri Jacques-Félix and Otto Stapf on grasses
– John William Bews’ book on grasses worldwide
– Studies by N.N. Tsvelev and D.M. Brandenburg on caryopses in the Gramineae family

Characteristics:
– Caryopsis is a simple fruit, monocarpellate, and indehiscent
– Resembles an achene with fused pericarp and seed coat
– Commonly known as a grain in the Poaceae family
– The hulls in many grains are flower bracts
– Dry fruit where fruit wall and seed are fused into a single unit

Varieties:
– Caryopsis diversity includes achene-like forms
– Berry-like forms found in some bamboo genera
– Nut-like forms in certain bamboo species
– Modified caryopsis with partially adherent pericarp
– True caryopsis with completely adherent pericarp

Botanical Significance:
– Caryopsis is the only fruit type found in the Gramineae family
– Different fruit structures proposed for grasses include achenes, nutricles, berries, and nuts
– Diverse forms of caryopsis represent caryopsis diversity
– Terminology used to distinguish caryopsis types
– Some botanists argue dry caryopsis is not a defining characteristic of the family

Caryopsis (Wikipedia)

In botany, a caryopsis (pl. caryopses) is a type of simple fruit—one that is monocarpellate (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 popularly called a grain and is the fruit typical of the family Poaceae (or Gramineae), which includes wheat, rice, and corn.

The term grain is also used in a more general sense as synonymous with cereal (as in "cereal grains", which include some non-Poaceae). Considering that the fruit wall and the seed are intimately fused into a single unit, and the caryopsis or grain is a dry fruit, little concern is given to technically separating the terms fruit and seed in these plant structures. In many grains, the "hulls" to be separated before processing are flower bracts.