Dictionary.com
Thesaurus.com

stomium

British  
/ ˈstəʊmɪəm /

noun

  1. the part of the sporangium of ferns that ruptures to release the spores

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Etymology

Origin of stomium

C20: via New Latin from Greek stomion , diminutive of stoma mouth