Origin: L, fr. Gr. A case to put anything in. See Tick a cover.
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. (Science: zoology) The chitinous cup which protects the hydranths of certain hydroids. The more or less cuplike calicle of a coral.
The wall forming a calicle of a coral.
A case or sheath especially a pollen sac or moss capsule.