New Zealand Silver Fern Propagation??

Never grown those particulare ferns, but have done a few in the past. This is the method I used (taken from a wonderful book on Ferns by Reginald Kaye)
Fern Spore Sowing.

The first, second and third essential is sterility of every part of the growing system (except perhaps the grower!).
This is the method I used and it worked for me, no doubt others will have their own system.
1.I use new plastic 7cm. plant pots and sterilise them by immersing them in boiling water for about a minute. (Test one first to make sure it does not lose shape. Otherwise you must cold sterilise with a mild bleach solution.
2. Any seed sowing compost is ok. Fill dry, cool pots to about an 1 cm below the top and firm down gently. Cover the top with a piece of kitchen towel or coffee filter paper. Pour boiling water through the paper. About a cupful will do.
3. Cover the pots and allow to cool. No further watering is necessary. Remove filter paper.
4. When cool sprinkle fern spores on the surface. Each pot will be big enough for about as many spores as you can fit on the tip of a penknife. They are very tiny and really do need to be spread thinly on the surface or they will not have room to develop. DO NOT DO THIS IN A WINDY SPOT! or sneeze.
5. Place pot in a plastic bag and seal. I use sandwich bags and the paper ties which come with the roll. If the surface appears to be drying out, gently mist with cooled bolied water.
6. Place in a warm (unless they are hot house ferns, in which case they need more heat) light position. A north facing or shady window ledge or in the greenhouse but put some shade netting over the top.
7.Eventually the surface of the pot will become covered in what looks like moss (if it is going to work). Open the bag and spray the surface of the 'moss' with distilled water( take the chill off it). Close the bag and put back in a warm, light area and wait.
8. If you have been successful, before long the moss will change to baby ferns. Gradually acclimatise them to growing outside the plastic bag.
9. Prick out the babies, I usually do this in little groups, you can always do it again when they are bigger.

 

Having looked more carefully at their instructions, I reckon you would get some growth in there, but it could be almost anything! For example, one bracken frond can produce enough spores such that if they all grew, every inch of land in the world would be covered! Those spores have been found floating in the air above the top of Mt. Everest! The air around us is stuffed full of fern and moss and liverwort spores, so that is what you would get.