 Some aquatic species of Marsilea , especially those growing with their rhizome submerged , may have vegetative leaves that are dimorphic . Some of their leaves grow up to the surface of the water , and look just like leaves of species growing out of water . These plants also produce other leaves with shorter leaf stalks that are not long enough to reach the surface , and so the leaflets remain underwater . These leaves have different anatomical and cellular characteristics better suited to their submerged environment . 
