( Wodehouse, 1935) The site of exit of the pollen tube from the sporoderm. See also: aperture. Exoexine ( Potonié, 1934) Synonym of sexine. Exogerminal (adj.) ( Batten and Christopher, 1981) Describing an aperture formed in the outer wall layer of the exine. Comment: This term, used in descriptions of pollen of the fossil Normapolles group, is essentially equivalent to ectoaperture.