The Families of Flowering Plants L. Watson and M. J. Dallwitz Callitrichaceae Link Habit and leaf form . Aquatic herbs . Leaves submerged, or emergent, or submerged and emergent. Leaf anatomy .
Minor leaf veins without phloem transfer cells.
Stem anatomy . Secondary thickening absent. Reproductive type, pollination . Plants monoecious, or dioecious. Sometimes pollinated by water.