05/27/2026
Blechnum penna-marina
Have a good look at the alpine water fern. In May, you can see that it has two kinds of leaves. The shorter, basal leaves are evergreen. The upright leaves that look like an old-style quill pen are spore bearing and deciduous (the name penna-marina refers to the resemblance to a sea pen, a fleshy, colonial marine organism; some species look like old-style quill pens). This is a classic feature of the genus Blechnum. Most ferns only produce one sort of leaf, and the spore producing apparatus is found on the backs of these. Unlike seed plants, ferns and their allies (Pteridophytesātare-id-oh-fites) reproduce by spores. While spores are somewhat resistant structures, the s***m and egg cells of ferns are delicate and extremely short-lived, and both spore germination and movement of the swimming s***m to the egg (to create an offspring fern) can only take place in a film of water. Note that seeds, in contrast, are capable of surviving long periods without moisture, and delaying germinating until conditions are optimal, which is why seed plants are as successful as they are.
Nevertheless, ferns, which predate seed plants by some 20 million years (ferns evolved around 390 million years ago), have exploited a huge variety of habitats, even arid ones. In those cases, reproduction is timed to coincide precisely with seasonal rainfall. Many ferns, including this one, are adaptable and exceptionally widely distributed. Alpine water fern is native to SE Australia, New Zealand and across the Pacific Ocean to South America. The subspecies alpina, which you see here, is a smaller version of the species, restricted in its distribution to New Zealand, Australia and the Subantarctic islands.
