Gunnera leaf. Close-up of a leaf of the gunnera plant (Gunnera manicata). The main vein (midrib) runs from lower left to right. This branches off to form other veins in the vascular system for food and water transport around the leaf. Gunnera originated in South America and is now grown for its large leaves of up to 2 metres across. Its midrib has large spines, some seen at lower centre.