What is "aril"

Aril \Ar"il\, ||Arillus \A*ril"lus\, n. [From LL. arilli dry grapes, perh. fr. L. aridus dry: cf. F,. arille.] (Bot.) A exterior covering, forming a false coat or appendage to a seed, as the loose, transparent bag inclosing the seed of the white water lily. The mace of the nutmeg is also an aril.
--Gray.

"accessory covering of seeds," 1794, from Modern Latin arillus, from Medieval Latin arilli, Spanish arillos "dried grapes, raisins."

n. A tissue surrounding the seed in certain fruits such as pomegranates.

n. fleshy and usually brightly colored cover of some seeds that develops from the ovule stalk and partially or entirely envelopes the seed

An aril (pronounced ), also called an arillus, is a specialized outgrowth from a seed that partly or completely covers the seed. An arillode or false aril is sometimes distinguished: whereas an aril grows from the attachment point of the seed to the ovary (from the funiculus or hilum), an arillode forms from a different point on the seed coat. The term "aril" is sometimes applied to any fleshy appendage of the seed in flowering plants, such as the mace of the nutmeg seed. Arils and arillodes are often edible enticements, encouraging transport by animals and thereby assisting in seed dispersal. Pseudarils are aril-like structures commonly found on the pyrenes of Burseraceae species that develop from the mesocarp of the ovary – the fleshy, edible pericarp splits neatly in two halves, then falling away or being eaten to reveal a brightly coloured pseudaril around the black seed.

The aril may create a fruit-like structure (called a false-fruit). False fruit are found in numerous Angiosperm taxa. The edible flesh of the longan, lychee, ackee and lleuque fruits are highly developed arils surrounding the seed rather than a pericarp layer. Such arils are also found in a few species of gymnosperms, notably the yews and related conifers. Instead of the woody cone typical of most gymnosperms, the reproductive structure of the yew consists of a single seed that becomes surrounded by a fleshy, cup-like covering. This covering is derived from a highly modified cone scale.