Dispersal of tree seeds by water, as in the case of certain water plants, occurs less frequently. Of the European trees the older is one whose seeds are dispersed by water as well as by the wind, and of the tropical species the coconut palm is a noteworthy example.

The small seed of the alder is equipped with air sacs that keep it afloat on the water surface for weeks until the spring floods carry it far afield. The coconut palm, now mild on the shores of continents as well as tropical islands, was brought to these places by sea currents and the regular swell of the ocean. But over long distances man also played its part.

Fruits that fall on the shore are carried to the sea by the needing tide, then borne great distances by the currents to be thrown up again by the incoming tide on the shores of other Itihinds and continents.

The fruits of broad-leaved trees are classified as true fruits if their origin is a single ovary, or accessory fruits if other parts of the flower are involved, or if their origin is the entire inflorescence (mulberry).

For example, pioneer trees such as the birch, aspen, alder and pine, which are the first to occupy wide, treeless expanses, produce a vast quantity of seeds which are very light a lid adapted for flights of hundreds of metres or even kilometres. That is how young trees may spring up in places where no withstand both heat and frost, and have moderate soil requirements, while their rapid early growth enables them to win the battle against surrounding grasses and other vegetation. They begin bearing seeds at an early age and thus rapidly fill the surrounding area with their offspring.

On the other hand, shade-tolerant trees such as beech and oak, whose offspring can thrive in shade and appreciate the protection of the surrounding forest in their first years, have heavier seeds that do not fall far.