This is a direct scan of the upper and lower sides of two fronds of P. amorphum combined into one image. The fronds were collected on July 12 2006 from a plant at the above location. Note the round sori and blunt pinnae; these features help to distinguish P. amorphum from the closely related P. hesperium.
The species is distinguished from the similar P. calirhiza by the long -attenuate tips of the pinnae, round sori, and free veins. P. calirhiza usually (but not always) has at least some anastomosing veins. P. glycyrrhiza prefers more shade and damper sites, as seen here.