Two large genera worthy of note are Blechnum and Asplenium. There are about 15 species of the genus Blechnum in New Zealand, mostly ferns with simple leaflets (pinnae). The Cape Blechnum, B. capense, is a feature of the landscape almost everywhere, on roadside cuttings and banks of streams. The young fronds are of reddish colour, and mature fronds may grow to nearly 10 ft. B. discolor has stiff, green fronds, whitish below, and it spreads freely by stolons. The same habit of vegetative reproduction is seen in the “miniature tree fern”, B. fraseri, with a small crown of leaves several feet above the ground. B. filiforme has a juvenile form with small, rounded leaves, but the mature form is a climber with long, pointed, sterile fronds, up to 30 in. long, and very narrow fertile fronds. B. membranaceum, B. lanceolatum, and the large B. norfolkianum are closely related forms. Two seaside species, B. durum and B. banksii, are common, especially in the south. Throughout the genus the fertile fronds are very narrow, purely spore bearing, and differ greatly from the sterile fronds which provide the food for the plant.
Closely related to Blechnum is Doodia, two species of which are common. In the north D. media covers whole hillsides with its autumn coloured fronds. D. candata is smaller, not so common, and found only in the North Island.
There are about 15 species of spleenworts, genus Asplenium. Some of these have simple leaflets, as A. lucidum, the beautiful widespread shining spleenwort, and the shore spleenwort, A. obtusatum. Among species with more divided fronds is the hen and chickens, A. bulbiferum, which bears tiny young plants on the surface of the frond. The somewhat similar A. lamprophyllum contains oil of wintergreen. A. flaccidum is found in several forms; it may grow erect from the ground, but is best known as it hangs from the branches of trees with long, narrow, drooping fronds of a leathery texture.
There are in New Zealand five species of the shield fern, genus Polystichum, one of which has been reported only from Kapiti Island. The scaly shield fern, P. vestitum, forms a prominent feature of forest, especially in the south, where its dark-green leaves form a spreading crown up to 6 ft across. P. sylvaticum is smaller, while P. cystostegia, with rather pale-green fronds, is found in alpine regions. P. richardii is very dark green, harsh to the touch, and the large, rounded sori are covered by an indusium with a central black spot. This species is fairly common, and often found near the sea.
The genus Lastreopsis is represented by the widespread hairy fern of the forests and the velvet form, L. velutina, of dry places. L. glabella and L. microsona have similar finely cut fronds.
Six species of maidenhair ferns are found in New Zealand, the most common of which are Adiantum cunninghamii and the closely related A. fulvum. Growing in the sun is A. aethiopicum and A. hispidulum, with bristly hairs and autumn coloured young fronds. The large A. formosum is found in only a few places in the North Island, while A. diaphanum is a modest little form common in shady places.