Within the nearly sopping wet subtropical low elevation forests of southern Japan one can easily find ferns growing not only in the ground, but also on every imaginable perch. This article focuses on four species that are found either growing on rocks (lithophytic habit) or on trees (epiphytic habit), but that can also colonize soils, in particular the moist or even wet ground near mountain streams.
As one might expect, such places give the impression of the lushness of a tropical rain forest, however such forests are in fact temperate, albeit with a strong influence of subtropical flora. First, we’ll look at the genus Neocheiropteris, represented in the forests of Fukuoka Prefecture by two species, N. enstata, and N. subhastata, the former being a conspicuous ground and rock fern in many forests while the latter showing itself to be a shy cousin with great flexibility in habitat choice.
N. enstata at first glance might be mistaken to be a species of Pyrrosia. That is what I thought it was the first time I saw it. It grows either as a lithophyte or terrestrially, but always in a place with abundant water (one thing that sets it apart from Pyrrosia which like drier sites).
Along streams it can form lush mats on top of flat rocks, however, it is just as happy to grow in the ground. I’ve not seen it growing as an epiphyte in the Fukuoka area, but in exceptionally wet climates it could possibly grow in trees. Occasionally colonies can be continuous carpets of fronds. Another place you sometimes find it is on rocks on seepage slopes. Here the plants never dry out and in fact the roots are nearly under water much of the growing season. The large, broad shiny leaves are deeply ribbed making it an attractive plant. The round, naked sori are in lose pairs on either side of the midrib of the frond, a diagnostic feature. It is usually seen at low elevations, not more than 400 meters high in the Fukuoka area.
A far rarer fern than its common relative, N. subhastata can be found growing low on trees, on rocks, and also in the ground. I first found it growing low on trees next to a stream, and even growing on dead bamboo canes. At first I thought it was Microsorium buergerianum, a fern it closely resembles, although when seen side by side the differences are obvious. These plants had simple elongate fronds with undulating margins and sori resembling both Microsorium and N. enstata. Further upstream from these was a colony of very small ferns with distinctly triangular fronds growing over a mossy rock surface and terrestrially. I immediately remembered seeing this fern in a picture and guessed it to be N. subhastata.
I returned time and again to look for spore on these plants, but I could never find any. One day, a little further downstream, I saw some of this same triangular frond fern growing in humus on a huge boulder. I followed its trailing rhizome and remarkably as it grew out of the humus and became a true lithophyte on the rock surface, the fronds “turned into” the elongate frond fern I found downstream. I immediately saw my mistake and realized that this was indeed one species with two distinct frond types.
The terrestrially growing fronds are short, triangular, and sterile while the lithophytic or epiphytic fronds are elongate and fertile and have a small auricle on one side of the base of the frond. Like E. enstata, the sori are in round and naked in lose pairs on either side of the midrib of the frond. This is a much smaller species than N. enstata, so the two cannot be confused. This species seems to require high humidity to survive. I’ve only seen it at low elevation, ~300 meters or less.
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