 The leaves are the most easily observed characteristic for the Marsileaceae ; they have a long slender leaf stalk ending in zero , two , or four ( occasionally six ) leaflets . The number of leaflets differs among the three genera and can therefore be used for identification . In Pilularia , the leaves are narrowly cylindrical and taper to a point . Leaves of Regnellidium bear two broad leaflets , while leaves of Marsilea bear four leaflets at the tip . The four leaflets on the leaf of Marsilea are not borne equally . Instead , they are borne in pairs with one pair of leaflets attached slightly higher than the other . Thus in the developing leaf , the leaflets are folded more like the wings of a butterfly than like the leaflets of a clover . 
