endothecium

noun, plural en·do·the·ci·a [en-doh-thee-shee-uh, -see-uh] /ˌɛn doʊˈθi ʃi ə, -si ə/. Botany.

1. the lining of the cavity of an anther.
2. (in mosses) the central mass of cells in the rudimentary capsule, from which the archespore is generally developed.
3. (in bryophytes) the central mass of cells in the capsule, including the spores and columella.

noun plural -cia (-ʃɪə, -sɪə) botany

1. the inner mass of cells of the developing capsule in mosses
2. the fibrous tissue of the inner wall of an anther