A water gap is a small opening that forms on breaking of dormancy in physically dormant seeds or fruits. Gama-Arachchige et al. examine the development of the micropylar region of seeds of Geranium carolinianum and report on the ontogeny of the micropyle–water gap complex. Post-pollination development of the seed coat in G. carolinianum results in an anatomically specialized micropylar region that functions as the water gap.