ostiole

plural ostioles

1. biologyA small hole or opening through which certain fungi release their mature spores.

   1 more example

   The Erysiphacae may possibly have given rise to the Laboulbeniales, the only other group in which a single daughter cell of the oogonium is responsible for the asci, and perhaps to the lower Pyrenomycetes also; these, like the Erysiphaceae, have regularly arranged asci, and in Chaetomium fimete the perithecium is without an ostiole.

   2010, Helen Gwynne-Vaughan, Fungi: Ascomycetes, Ustilaginales, Uredinales, page 54

2. biologyA similar hole or opening in plants, such as the opening of the involuted fig inflorescence through which fig wasps enter to pollinate and breed.