Sores along the central line of the pinnae, subelliptical and confluent when mature.

It hates the rain directly on its fronds, preferring the moisture comes to its roots through the soil soaked by seepage of rainwater.

For this usually grow well inside the crevices of the rocks and between the stones of the walls of the terraces, where no rain falls over.

It has two subspecies: one diploid, which is actually the original fern, Asplenium petrarchae ssp.

bivalens with a chromosome number of 2n = 72 and one autotetraploid by spontaneous doubling of their genome, Asplenium petrarchae ssp.