Trunk tall and slender, tapering from a swollen base; spathes numerous (7); inflorescence appearing in the axis of the rather persistent lower leaves, long and slender; staminate flowers arranged in rows.
Aeria.
Trunk robust or of uniform diameter; spathes 1 or 2; inflorescence short and brush-like, not exposed until the enclosing leaf below it falls away; flowers not set in rows.
Spathe single, the fruits 2.5 cm. long; leaf-divisions upright, very dark green.
Areca.
Spathes 2, fruits less than 1.25 cm. long; leaf-divisions horizontal or oblique.
Trunk robust, thickened near the middle; leaf-divisions inserted by twos and standing at different angles; inflorescence twice or thrice branched, standing close to the leaf-bases.
Roystonea.
Trunk slender, of uniform diameter; leaf-divisions at equal distances, horizontal; inflorescence once-branched, at maturity 15 cm. or more below the leaf-bases.
Acrista.