How are grass grains different from most other fruits?

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wild rice — Poaceae Wild rice (*Zizania aquatica*).

Grass grains, known botanically as a caryopsis, are distinct from most other fruits due to the unique relationship between their internal structures.

In a typical fruit, the seed is contained within the fruit wall (pericarp) and can often be separated from it. In contrast, the caryopsis is a specialized, dry, one-seeded fruit in which the fruit wall is completely fused or united with the seed coat. This tight adhesion makes it difficult to separate the two layers without employing special milling processes. While most other dry, indehiscent fruits—such as an achene—allow the seed to lie free within the cavity, attached only at a single point, the grass grain remains a single, inseparable unit.1234