ˌ ̷ ̷ ̷ ̷ˈ ̷ ̷s(h)ēəm noun
( plural amphithe·cia -ēə)
Etymology: New Latin, from amphi- + -thecium
1. : the external layer of cells surrounding the sporogenous tissue in the sporangium of a moss
2. : the inner layer of the perithecium next to the hymenium in certain lichens