Theca

n.	1.	A sheath; a case; as, the theca, or cell, of an anther; the theca, or spore case, of a fungus; the theca of the spinal cord.
	2.	(Zool.) The chitinous cup which protects the hydranths of certain hydroids.

Noun	1.	theca - a case or sheath especially a pollen sac or moss capsule Synonyms: sac
	2.	theca - outer sheath of the pupa of certain insects

cover, covering, natural covering, sac