Why must the plant which grows directly from the fern spore be wet?

so that the egg can be fertilized

so that it can grow

in order to produce a seed

Sperm have flagella, which are whip-like tails that allow them to swim. In order to swim, they need water. This means ferns can only successfully reproduce in wet places, or after a rain. After fertilization, the sporophyte grows up on top of the gametophyte.