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But no living plants have such cupules, and the fossils the researchers had found were of partially decayed plants, making thorough analysis impossible.

The fruit of the oak, being an oval nut growing in a woody cup or cupule.

The generally one-seeded nut-like fruit is associated with the persistent often hardened or greatly enlarged bracts forming the so-called cupule which gives the name to the group.

As development of the ovary and seeds progresses, the cupule also grows, and ultimately entirely surrounds the cluster with the hedgehog-like coat in which the nuts are contained when ripe.

In the Chestnut the cupule forms the bur; in the Hazel, a leafy husk.