Imprisoned Disk Flowers

This is a Black-eyed Susan from my Michigan native wildflower garden. It's in the composite family meaning it has two types of flowers in the flower head. The yellow "petals" are actually ray flowers, and the dark central disk is composed of tightly-packed small "disk flowers".

 

This is an unopened flower head, with the rays seemingly forming "prison bars" around the disk flowers. It would be completely opened the next day.

Done