Cupule

Cupule, the more or less cup-like structure surrounding one or more fruits in many trees, especially those forming the order Cupuliferae, such as the oak, beech, Spanish chestnut, and hazel. It is formed after fertilisation, as a ring-shaped out-growth from the peduncle. The cup of the acorn bears imbricate leaf-scales; the husk of the chestnut spinous rudimentary branches. This latter and that of the beech split downwards into four teeth as the enclosed fruits enlarge in ripening.