[nyanpasu64]

I recently learned that (Wikipedia) "Vascular cambia are found in all seed plants except for five angiosperm lineages which have independently lost it; Nymphaeales, Ceratophyllum, Nelumbo, Podostemaceae, and monocots.[1]" Four of these lineages are aquatic plants (including water lilies) and some scientists theorize monocots may have also evolved in the water. I seem to recall reading that aquatic plants don't "need" woody growth for structural stability, but can't find a source right now.