Green spheres on pond roots

Hi! I've been searching for days now! Please let me know what are those spheres. Volvox? Algae? Spawn of envy snail?

Thank you!

It could be Algae Sergie have you lifted one out of the water to look at it?

My Flickr photos

It does look like algae. When taken out it stays like a lump of jelly rather than like string algae would be.