Germinating sycamore (Acer pseudoplatanus) seed. A seedling is emerging from its split seed coat. The unfolding green tissues are the cotyledons of the embryo. The curved filament below them is the hypocotyl, a stem that terminates in the root below ground. The feather-like wing (above) shows weathering due to being on the ground over winter. Sycamore seeds are winged achenes (single-seeded fruits) known as samaras. Usually produced in pairs, they can be carried considerable distances on the wind when shed.