Hawaii - Nephrolepis

If I had to guess, I would say that the most common fern on Hawaii in terms of sheer biomass is Nephrolepis. There are several species in this genus on the Big island, and it is everywhere! Along roadsides, on lava, almost everywhere you look. It is truly ubiquitous. It's a lovely fern, with bright green fronds and very erect stature. The popular houseplant Boston Fern is also a member of this genus, and you can probably see the resemblance:

Here are some Nephrolepis growing in a tree mold in a lava field at Kilauea:

And immature (top) and mature (bottom) sori:

Hawaii - Pityrogramma

Another fern we found out on the lava in Hawaii was Pityrogramma austroamericana, a little bright green thing that has an interesting feature common in ferns that live in dry, challenging environments: farina. Farina is a powdery layer on the lower (abaxial) surface of the frond, which is usually white or yellow, and is thought to reflect light and therefore heat, cooling the frond. Many ferns in the deserts of the southwestern U.S. have farina, and it's a defining characteristic of several groups of ferns. This is one of the only farinose ferns in Hawaii.