Dan Crawford said:
No silly question on here...
That is normal, it's just the plant producing new leaves. The brown spots are "sporangia".
If i were you i would cut off the leaf with the roots growing on it (cut it as close to the base of the stem as possible) and leave the main plant to put it's energies into producing new growth from the rhizome (root).
You can keep the small, new plants and try and grow them on if you like. The leaf that you have snipped off could be partly tied to a rock of some other kind of hardscape. i wouldn't use the whole leaf since this will die off and look ugly and attract algae.
I hope this helps.
Dan
Dan's right that there's nothing to worry about, but the spots aren't sporangia unless they produce spores, not roots. The spores are a ferns method of sexual reproduction whereas the plantlets growing from the leaves are produced completely asexually without the alternation of generations that ferns must undergo to reproduce sexually.
If you don't like how they look or want the main plant to grow really well and look it's best, then snip the leaves off as they form.
However, if you want to grow loads more ferns though I'd leave the leaves until the new plantlets grow leaves and rhizomes and get to a decent size, then twist them off and secure to new wood/rocks. They will get going far quicker if they get more sustinance from the main plant when tiny. They'll grow eventually either way though - they're as tough as old boots!
Good luck.
