pipewort: aquatic perennial of North America and Ireland and Hebrides having translucent green leaves in a basal spiral and dense buttonlike racemes of minute white flowers
aquatic plant: a plant that grows partly or wholly in water whether rooted in the mud, as a lotus, or floating without anchorage, as the water hyacinth
mortarboard: a square board with a handle underneath; used by masons to hold or carry mortar