Picture of a hydrogamous plant

A few aquatic plants are pollinated under water. These are said to be hyp-hydrogamous. Plants using this pollination method rely on water to transport the pollen grains. We would be led to believe, that pollen of these species, would have good opportunity to be embedded in sediments and fossilized. On the other hand, grains of these species have very thin exines and consequently, the remains are not recognizable in the fossil record.