cupule

noun [抽象名词][植] 壳斗；吸盘；杯状凹；杯形托

In Spring, tiny flowers called catkins blossom, then develop into acorns, which form inside a cap called a cupule.
在春天，一种叫做柔荑花科花的小花内部一个被状物的小帽子会发育成为橡树果。