the world > plants > particular plants > cultivated or valued plants > particular food plant or plant product > edible pods, seeds, leaves, or flowers > [noun] > other edible seeds > manna-grass seeds (2)
the seeds of manna-grass (floating sweetgrass), Glyceria fluitans, formerly used as food in parts of Europe.
In full Poland (also Polish) manna. = manna seeds n. at compounds 2. Obsolete.