Arber’s happy phrase) “has won for them the freedom of the land.” The Seed Plants, then, achieved their wonderful abundance and variety owing to the highly stimulating conditions offered by a terrestrial existence; we must assign to all the existing types a long terrestrial ancestry. How, then, about the water plants whose leaves and flowers so decorate our lakes? There seems no doubt[13] that they are species which have left the land to resume the aquatic habits of their remote ancestors. With few exceptions they retain the aerial mode of pollination which is the pride of the specialized land plants. The pressure of competition has probably driven them into the water, where they descend as far as the lessening light-supply will allow. Some--presumably the earliest to take to an aquatic life--have all their relations to keep them company, the remote ancestor which adopted an aquatic habit being now represented by many species, or even by many genera. In other cases a terrestrial genus or order has few or only a single aquatic representative. It may be assumed that in such a case the aquatic habit has been recently acquired. The great majority of water plants send their flowers up above the surface to be pollinated by wind or (more rarely) by insects. It may be noted that few of the more highly evolved groups of Seed Plants are represented in the aquatic flora; wind-pollinated flowers of a rather primitive type of structure are the rule in our lakes and rivers; which points to an early assumption of the aquatic habit, and suggests that the land is more favourable than the water for the evolution of higher types.