There are two distinct stages in the life cycle of ferns. The first stage is that of the gametophyte.
Spores are produced on the underside of mature plants. These will germinate and grow into small, heart-shaped plants called gametophytes.
The gametophytes produce both sperm and egg cells, and will fertilize itself, or others. Once the fertilization occurs, the adult fern will begin growing.
The second stage in the life cycle of a fern is the adult stage. The fertilized gametophytes begin to look like a mossy growth.
After some time, young fronds will appear, rising out of the moss. If direct sunlight falls onto the young fronds for an extended period of time, the plant may die easily. This is because the tiny stems are not strong enough to sustain direct light and will dry out.
Once these tiny fronds grow larger, the plant has a better chance of survival. When the veins are matured, moisture from the ground will be transported easily to the outermost leaves and the plant can withstand periods of direct sunlight.
After the plant is large and mature, it will grow spores on the undersides of its leaves and the life cycle of a fern will begin again.