Tuatara: Volume 12, Issue 3, November 1964
Key to the New Zealand Filmy Ferns (Hymenophyllaceae)
Key to the New Zealand Filmy Ferns (Hymenophyllaceae)
For the Purpose of this key the family is divided into the original genera Trichomanes (L) and Hymenophyllum (Smith). This division follows the classification used by Allan (1961). although the sub-genera he proposed are not used. In dividing the two original genera into sub-genera Allan followed the work of Copeland (1938) who considered these genera to be unnatural groupings and divided the family into 33 genera, 13 of which are present in New Zealand. Both the names and taxonomic characters used in defining the latter are the same as those used by Allan when defining sub-genera. The original division of the Family is retained for simplicity and vegetative characters are used where possible, for ease and ready application of the Key. Readers are referred to Allan (1961), and Dobbie and Crookes (1952) for the synonymy.
The Family as a whole has over 650 species which have a world-wide distribution and according to some authors an Antarctic origin. However most species today have a sub-tropical or warm temperate distribution growing in areas of high rainfall and humidity. However, as they are usually epiphytes the amount of available water varies considerably even within this environment and they have a wide range of modifications both in vegetative form and structure adapting them to these conditions. Copeland goes so far as to say that this range exceeds that of any other family, which is rather surprising as all the plants appear to be of basically simple form.
There are twenty-one species of the genus Hymenophyllum in New Zealand, fifteen of which are endemic. H. peltatum, found throughout New Zealand, is also found in Norway and France, H. ferrugineum is found in Chile and H. rarum and H. flabellatum in neighbouring Australia. These all reflect the Family's world-wide distribution. Within New Zealand most of the species are spread throughout the three main islands growing in areas of fairly high rainfall and humidity, but a few are restricted. For instance, H. minimum is found only in the South and Stewart Islands while H. montanum has been recorded only from the mountains near Lake Wakatipu; neither H. atrovirens nor H. malingii have been recorded from Stewart Island, but on the other hand, H. villosum and H. multifidum grow as far south as Campbell Island, the latter also being found in the Auckland Islands. There is also a scattering of species on the northern off-shore islands and on the Chathams.
Although most species range from lowland to montane forests, either growing terrestrially or epiphytically, H. malingii is very selective in its habitat. It prefers to grow on dead Libocedrus trunks and is only occasionally found on trunks of other trees. Of all the New Zealand species H. multifidum has the largest altitudinal distribution, ranging from lowland forests where it grows epiphytically, to alpine scrub areas where it is usually terrestrial. Others such as H. dilatatum have a wide latitudinal range and are found from the Three Kings Islands in the north to Stewart Island in the south. Collectively the above illustrates the wide variety of habitats in which the genus grows and correlated with this is a variation in vegetative characters. The fronds of H. multifidum are a good example of this, for in an alpine environment they are curled and only a couple of inches in length, while when growing epiphytically in the lowland forest are six to eight inches long and quite straight. Both the degree of hairiness and size of the flange on the stipe and rachis also vary, especially in H. sanguinolentum. Similar variations occur in other species. Hybridisation between H. demissum and H. flabellatum and H. rufescens. H. peltatum and H. revolutum, and H. sanguinolentum and H. villosum have all been recorded and this has led to further character variation.
Two species of Hymenophyllum are not included in the Key. One, H. australe recognised by Copeland was included by Allan in Hymenophyllum flexuosum and following this no distinction between the two species is recognised here. The other. H. hirsutum, was described by Hooker in the early days of New Zealand botany but no further specimens have been collected or recognised. Allan includes it in the ‘Flora’ adding that the specimens from which it was named might not even have come from this country.
.jpg)
Plate 1
Fig. 1:
Trichomanes endlicherianum: Note the tubular indusium of the sorus immersed in the bottom segments of the pinnae and the long exserted receptacle. Fig. 2:
Hymenophyllum dilatatum: Note the bivalved indusium of the sorus partly immersed and borne terminally on the frond. Fig. 3: The stipe of
H. afrovirens showing the characteristic straight wing narrowing toward the base. Fig. 4: The stipe of
H. flexuosum showing the characteristic crenulate wing. Fig. 5:
Hymenophyllum minimum. Note the pinnatifid frond with toothed margin and the hair-like unwinged stipe. Fig. 6: A portion of the frond of
Hymenophyllum revolutum showing its bipinnatifid nature and toothed margin.
Key to the Genera
Indusium bivalved and cup shaped, receptacle rarely exserted | Hymenophyllum |
Indusium tubular, usually immersed in the lamina, receptacle long and prominently exserted | Trichomanes |
Key to the Genus Trichomanes
1 | Fronds borne in tufts | — 2 |
Fronds borne on a creeping rhizome | — 3 | |
2 | Fronds oblong, veins of pinnae unbranched | T. strictum |
Fronds triangular, veins of pinnae branched | T. elongatum | |
3 | Frond kidney shaped and undivided | T. reniforme |
Frond divided | — 4 | |
4 | Veins branching freely in the segments of the lamina, lamina light green | T. venosum |
Veins simple or forked, lamina dark green | — 5 | |
5 | Sori stalked, lamina delicate | T. colensoi |
Sori immersed in the bottom segments of the pinnae | T. endlicherianum |
Key to the Genus Hymenophyllum
1. | Stipe definitely winged to base | — 2 |
Stipe not winged or only partly so | — 4 |
.jpg)
Plate 2
Fig. 7: The sorus of
Trichomanes endlicherianum. Note the tubular indusium and the protruding receptacle. Fig. 8: The sorus of
Hymenophyllum dilatatum borne terminally on the frond. Note the entire margins of the bivalved indusium. Fig. 9: The sorus of
Hymenophyllum revolutum borne in the axis of a pinna. Note the toothed margin of the indusium. Fig. 10: The sorus of
Hymenophyllum multifidum borne laterally. Note the crenulate nature of the indusium and the partly exserted receptacle.
References
Allan, H. H., 1961. Flora of New Zealand, Govt. Print. Wellington, N.Z. Copeland, E. B., 1938. Genera Hymenophyllacearum. Phil. Jour. Sci. Vol. 67 No. 1. pp. 1-110.
Dobbie, H. B., and Crookes, M., 1952. New Zealand Ferns. Whitcombe and Tombs Ltd., 5th Ed.