A cardinal organ part (PO:0025001) that is composed of the outer layers of a sporangium (PO:0025094) and bounds the archesporium (PO:0030074) or plant spores (PO:0025017). [source: ISBN:9780070588493]
Comment
May have multiple layers such as exothecium, endothecium and tapetum. Early in development, the sporangium wall bounds the archesporium. Later, after spores develop from the archesporium, it bounds the spore or spores.