theca
/ˈθiːkə/
noun
- A case, covering, or sheath, especially in biology, such as the outer layer of a coral polyp or the wall of a plant spore.
- Under the microscope, the theca of the spore appeared thick and ridged.
- Scientists examined the theca to understand how the ancient plant reproduced.
- The coral's theca protects the soft body of the polyp inside.