cupule
noun
cu·pule ˈkyü-(ˌ)pyül 
: a cup-shaped anatomical structure: such as
a
: an involucre characteristic of the oak in which the bracts are indurated and coherent
b
: an outer integument partially enclosing the seed of some seed ferns
Example Sentences
Recent Examples on the Web Until now, researchers had focused on a fossil cupule plant called Caytonia, discovered in Yorkshire, U.K., as the closest relative to angiosperms. 
Elizabeth Pennisi, Science | AAAS, 26 May 2021 The team found that, as with the outer seed coat in modern angiosperm seeds, the cupule tissue curved around the developing seeds. Elizabeth Pennisi, Science | AAAS, 26 May 2021
Elizabeth Pennisi, Science | AAAS, 26 May 2021 The team found that, as with the outer seed coat in modern angiosperm seeds, the cupule tissue curved around the developing seeds. Elizabeth Pennisi, Science | AAAS, 26 May 2021 Word History
Etymology
New Latin cupula, from Late Latin, diminutive of Latin cupa tub — more at hive
First Known Use
1826, in the meaning defined above