aril

Seed vessel pyramidal, containing many seeds enveloped in an elastic aril by which they are ejected when the fruit opens.

From The Medicinal Plants of the Philippines by Jerome Beers Thomas

The fruit is about the size of an ordinary walnut, with a thick rind, which, upon opening, at maturity, discloses a reddish aril covering the nut within.

From The Nut Culturist A Treatise on Propogation, Planting, and Cultivation of Nut Bearing Trees and Shrubs Adapted to the Climate of the United States by Andrew S. Fuller

But on closer inspection we observe that the flower stalks are combined into little groups, each group occupying the aril of one of the basal leaves.

From Species and Varieties, Their Origin by Mutation by Hugo de Vries

The aril which surrounds the seed and the roots of Sapindus Saponaria, an evergreen tree, I have seen used as soap in South America and the West Indies under the name of soap berries.

From The Commercial Products of the Vegetable Kingdom Considered in Their Various Uses to Man and in Their Relation to the Arts and Manufactures; Forming a Practical Treatise & Handbook of Reference for the Colonist, Manufacturer, Merchant, and Consumer, on the Cultivation, Preparation for Shipment, and Commercial Value, &c. of the Various Substances Obtained From Trees and Plants, Entering into the Husbandry of Tropical and Sub-tropical Regions, &c. by P. L. Simmonds

Fruit ribbed, long, the compartments formed by reticular partitions; contains many irregular seeds, one border sharp, the other obtuse, covered by a very thin aril.

From The Medicinal Plants of the Philippines by Jerome Beers Thomas