:''Distinguish from
aryl, which is a type of organic chemical radical.''

Close-up of pomegranate arils - The seed can be seen inside the translucent flesh.
An 'aril' (or 'arillus') is a fleshy covering of certain
seeds formed from the '''
funiculus''' (attachment point of the seed).
The aril may create a
fruit-like structure (called a ''false-fruit'') and is produced by a few species of
gymnosperms, notably the
yews and related
conifers in the
families Taxaceae and
Cephalotaxaceae. Instead of having a
woody
cone as is 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.
In the photographs of a European yew (''
Taxus baccata'') at right and below, note that the aril starts out as a small, green band at the base of the seed, then turns brown to red as it enlarges and surrounds the seed, eventually becoming fleshy and scarlet in color at maturity. The aril is attractive to fruit-eating
birds and is non-toxic (all other parts of the yew are toxic), serving therefore to promote dispersal of the yew seed by birds, which digest the fleshy aril as a food source, and pass the seed out in their droppings.

The fleshy aril which surrounds each seed in the yew is a highly modified seed cone scale.
The term ''aril'' is not limited to yews. It means any specialized outgrowth from the funiculus (or ''hilum'') that covers or is attached to the seed. It is sometimes applied to any appendage or thickening of the seed coat in
flowering plants, such as the edible parts of the
mangosteen and
pomegranate fruit, or the
mace of the nutmeg seed. The edible flesh of the
longan,
lychee, and
ackee fruits is a highly developed aril surrounding the seed rather than a
pericarp layer.
See also
★
Elaiosome
References
★ Anderson, E. & Owens, J. N. (2003). Analysing the reproductive biology of Taxus: should it be included in Coniferales? ''Acta Hort.'' 615: 233-234.