Sporangia either not borne on the blade of a frond but instead on separate fronds or divisions of fronds without blades, or concealed in roundish, thickened, greatly reduced and modified divisions of fronds very different from the green sterile fronds or pinnae.


Sporangia borne in sori on the lower surface of green, +/- flat blades of fronds; fronds or pinnae sometimes moderately dimorphic, but, if so, the fertile ones not modified into round, capsule-like divisions that conceal the sporangia.