Plural of cupule; small cup-shaped structures or cavities, especially the cup-like base that holds an acorn in an oak tree.
From Latin cupula meaning 'small cup,' diminutive of cupa 'cask or barrel.' The term evolved in botany to describe the characteristic cup-shaped protective structures found in various plants.
Nature uses these tiny botanical cups as architectural masterpieces—acorns sit snugly in oak cupules like eggs in cartons, protecting seeds while remaining easy to scatter. This same cup-shape appears across thousands of plant species, suggesting evolution found this design so efficient it kept reusing it.
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