Two distinct adult leaf forms, i.e., land and submerged leaves, of the aquatic fernMarsilea vestitawere collected from nature and were obtained from plants in sterile culture. The venation patterns and anatomy of these 2 adult leaf forms are presented in detail. Pinna development and the morphology of a third leaf form, i.e., floating leaves, are briefly considered. The differences in leaf form are ascribed to differences in the activity of the marginal meristem of the leaf.