What Is an Acorn Cupule?

The top of the acorn that resembles a hat or a cap is called the cupule. It's a tough outer shell that can be either prickly and rough or scaly and smooth. Its purpose is to provide an extra layer of protection for the delicate embryo enclosed by the kernel, which itself consists of two fatty leaves called cotyledons.

Is an acorn a fruit or a nut?

Chestnuts, hazelnuts, and acorns are examples of true nuts. Most people consider walnuts, pecans, and almonds to be nuts, also, but they are actually the seeds of drupes. A drupe, like a peach or cherry, has a fleshy fruit that surrounds a hard pit with a seed inside.

What is an acorn classified as?

An acorn is technically a fruit because it houses a seed, but due to its hard outer shell it's classified as a nut. This nut is specific to trees in the Quercus genus, collectively referred to as oaks.