Cyathea spinulosa and Common fern

[silverhair]

I see little difference between the 2 plants.

left:Cyathea spinulosa right: common fern

[SeanHoutman]

Ferns have a basic plan for the fronds, and there isn't much variation. I see that the C. spinulosa has a more elongate-lanceolate-attenuate shape for the secondary divisions, while your common fern is broadly lanceolate for the same division. Fern genera are based much on the shape, position, and nature of their spore producing parts, called sporangia, and whether or not there is a cover over them called an indusium. Look at the underside of the fronds to see them.

[silverhair]

Thank you Sean, yes, I found sporangia under the leaf of mature ferns.