• (n.) The inner lining of an anther cell.
En`do·the'ci·um noun [ New Latin See Endotheca .] (Botany) The inner lining of an anther cell. 
endothecium The inner tissue of an anther or a moss capsule.
the lining of the cavity of an anther. · (in mosses) the central mass of cells in the rudimentary capsule, from which the archespore is generally developed. · (in bryophytes) the central mass of cells in the capsule, including the spores and columella.