The term ARIL refers to a specialized seed covering found in some plants. It is a fleshy or hairy outgrowth that covers the seed and can be either partially or completely fused to the seed coat. The seed case is the outermost layer of the seed, which protects the embryo and other parts of the seed from damage. The seed coat is the innermost layer of the seed, which provides protection and nourishment to the embryo.