How does the cupule of an oak differ in origin from the husk of a birch?

In the plant order Fagales, the cupule (or hull) that surrounds the fruit is believed to have different evolutionary origins depending on the family.

• Oak (Fagaceae): In the genus Quercus, the cupule is derived from a highly modified and reduced branch system, along with its associated modified leaves or bracts.1
• Birch (Betulaceae): The husks in this family are thought to be composed of several modified bracts.1

While these structures serve a similar purpose in protecting the fruit, their developmental pathways reflect the distinct evolutionary histories of these two families within the order.1