A portion of plant tissue (PO:0009007) that is the internal part of a sporangium (PO:0025094), bounded by the sporangium wall (PO:0025306), and has as parts archesporial cells (PO:0030056). [source: ISBN:8122407927, ISBN:9780003686647]
Comment
Gives rise to sporocytes and may give rise to other sterile cells such as elators.