I have this narrow leaf java fern. I bought it pretty much dead because I wanted it 50% off. so, it has been sitting my tank for a few months not doing anything, not growing, not getting any deader. then, just a while ago i noticed this little plant growing on the other side of my tank. it was a single tiny leaf growing out of a black thing. it looked like the a chunk from the end of a broken stem, or something, but not like a seed. I was totally baffled as to where it came from, but i planted it in the sand.
a while Later, I pulled up the java fern to see if it had grown roots or anything. It hadn't but I saw that it was tied up with black string at the base so I thought i'd untie it. in the process, i basically...ripped the plant apart...oops.
anyway, for some reason I didn't take the dead leaves, and when i looked into the tank the next day, each leaf had 1-3 baby leaves growing out of the side of it! I buried all of the leaves flat in the sand and now I have lots of healthy green java fern babies. that's what the other baby i found was too!
so, the point is that if you are pruning your java fern, or find dead leaves, don't toss em', plant em'!
this is the best form of propogation that I have found so far!