There are no seeds, no cuttings, just spores released from the sori on a frond's underside. If the spores settle in a perfectly hospitable spot, they grow into prothallia, which look like liverworts. In time, both male and female gametes are produced. The mingling of those cells, via dew or splashing rain, continues the growth process. Success rates are low in the wild, which is why ferns make millions of spores.
In a kitchen window, odds are better. Commercial African-violet potting mix, three-quarters of an inch deep in a one-pint clear plastic deli tub, will work. Everything must be impeccably clean. I zap moistened medium in a heat-proof container in the microwave for 10 minutes or until an inserted instant-read thermometer reads above 180°F. I pour boiling water over and in the washed container and lid. This will be a closed environment and there's no point in growing mold.
You can purchase spores or collect them from your own plants. To do this, cut a frond with ripe sori and lay it on a piece of plain white paper in a breeze-free spot overnight. Carefully lift the frond to see a "print" of fern spores. Gently fold the paper in half, rocking it side to side to collect the spores. Next, take the paper to the trash and pour the spores into the bin; enough of them will be caught in the fibers of the paper to sow.
Steps for success
1. Sow Remove the lid of the prepared container (see above text), hold the paper spore-side down over the top, and tap the back. Reseal the tub at once.
2. Grow Place the tub in a warm place with very bright light but out of direct sun. In most cases, the medium will not have to be rewet. Depending on the species, the surface of the mix will turn green in weeks or months. Next, little green disks (prothallia) will appear.
3. Shift Tiny "sporlings" will develop with a frond or two that resemble the adult fern's. A plastic knife can be used to transplant them, about 12 sporlings per nursery tub of sterilized medium. Seal the tubs. If the medium begins to dry out, moisten it with distilled water.
4. Wean When the little ones look like miniature ferns, they can be moved to their own small pots. Place the pots in a plastic box and leave the lid slightly more open each week, until the young ferns are fully adjusted to open air.