Annotated Keys to the Tree Ferns and Some of Their Common Epiphytes in the Auckland Region
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TANE 29, 1983 ANNOTATED KEYS TO THE TREE FERNS AND SOME OF THEIR COMMON EPIPHYTES IN THE AUCKLAND REGION by J. E. Braggins Department of Botany, University of Auckland, Private Bag, Auckland SUMMARY Keys to the tree ferns of the Auckland area, the genus Tmesipteris and some common epiphytic filmy ferns are presented. Each key is followed by brief descriptive notes on the species, and some of the diagnostic details are illustrated. INTRODUCTION This account covers the tree ferns and two groups of their most frequent epiphytes in the Auckland area: the genus Tmesipteris and the filmy ferns. For each group a simple dichotomous key is followed by a few notes to assist in confirming the identification. Nomenclature follows Allan (1961) except for Tmesipteris, which follows Chinnock (1975). Note that the nomenclature of Cyathea has been revised (Tyron 1970) and the alternative names, although not accepted by some authors, are given in brackets in the notes. Some additional useful references have been included in the reference list. THE TREE FERNS The forest patches near Auckland have relatively few species of tree ferns compared to some areas of New Zealand. The scene here is dominated by the fast growing mamaku {Cyathea medullaris) and wheki {Dicksonia squarrosa) with ponga {Cyathea dealbata) usually present as scattered individuals. The fourth species Cyathea smithii is a plant of cooler places most frequently encountered at higher levels in the Waitakere Ranges whilst the fifth Cyathea cunninghamii (gully fern) is found scattered in stream gullies throughout the area. The following key uses only the major characters but further notes are given to assist confirmation of identification. Key 1: tree ferns 1. Son marginal, in part protected by the recurved margin ( (Fig. le); hairs (single rows of cells) copious and very large Dicksonia squarrosa Sori superficial, not directly associated with the margin (Fig. lg, h); scales (many cells in width) copious and large Cyathea spp. 2 2. Crown producing many fronds, the bases of the stipes narrow, only a small fraction of the diameter of the trunk, scales pale to red brown, stipe bases persistent on 193 trunk 3 Crown producing relatively few fronds with broad bases to the stipes which are up to one third diameter of trunk, stipe bases falling leaving only the scars, scales dark brown to black 4 3. Frond with a conspicuous white waxy coat on underside also present on stipes which are pale glaucous. Stipe bases only persistant, indusium delicate but often complete (Fig. If) Cyathea dealbata Frond pale green underneath, stipes and rhachis persistent hanging in an open skirt. Sori with a delicate cup-shaped indusium (Fig. lh). Frond of very soft texture Cyathea smithii 4. Plant massive with very large, arching fronds. Stipe bases persistant only in young plants otherwise most of trunk clean with abscission scars. Trunk usually 15 cm or more in diameter most of underside of frond bearing small sharply setose scales (Fig. lg) Cyathea medullaris Plant slender, very tall in relation to trunk diameter which is usually 10 cm or less. Fronds bearing small stellate hairs Cyathea cunninghamii Notes on tree ferns Dicksonia squarrosa. The presence of hairs (straight simple and large) and relatively harsh fronds separate the dicksonias from the cyatheas. Only D. squarrosa is found in Auckland though the other two species are sometimes planted. D. fibrosa is distinguished by its massive trunk (even fatter than the cyatheas) and lanceolate frond with pinnae to the base, (D. squarrosa has a short but definite stipe) and the hanging skirt of complete dead fronds. D. lanata is usually prostrate and has broad deltoid fronds on very long stipes. Cyathea dealbata (synonym: Alsophila tricolor (Col. ) Tryon). The white underside is very characteristic but very small plants may lack it then the rather glossy upper surface and broadly triangular frond of the juvenile may help. The red-brown scales of the adult are characteristic especially when compared to the pale scales of Cyathea smithii and the nearly black ones of mamaku. Cyathea smithii (synonym: Alsophila smithii (Hook, f. ) Tryon). Here the fond is pale green especially when viewed against the light. The frond is very soft to the touch and the hanging skirt of stipes and rhachises which have lost their lamina is quite characteristic. Small red- brown stellate scales are characteristic and if fertile the sori with their cup-shaped indusia also help. Cyathea smithii is only found in the higher hills. It is the only tree fern that could be confused with Dicksonia fibrosa, but the dead fronds of that species retain their lamina. Cyathea medullaris (synonym: Sphaeropteris medullaris (Forst. f. ) Bernh. ). As well as its size and shape and the clean trunk, this common tree fern has characteristic scales with dark tipped setae on their margins. These scales are found all over the underside of the frond and usually a few persist even on dead fronds. The indusium is complete though mostly lost on dead fronds. The dead fronds themselves usually soon drop leaving a clean trunk, although young plants may have an untidy mess of fronds where they cannot fall clear. The size and presence of setose scales are among the best characteristics to 194 distinguish this from Cyathea cunninghamii. Cyathea cunninghamii (synonym: Alsophila cunninghamii (Hook, f. ) Tryon). A very slender tree fern not particularly plentiful especially when compared to the ubiquitous mamaku to which in many ways it is rather similar. Usually noticed because it is more slender than mamaku and the fronds are less regularly arched. The stellate hairs on the frond are characteristic and the spore ornamentation also differs. TMESIPTERIS Tmesipteris is a genus of relatively small plants with simple or dichotomously branched stems bearing lateral leaves. They are usually epiphytic (though most species may occur on the ground and some do so regularly). They are of interest particularly because of their generally accepted relationship (or at least similarity) to some of the earliest land plants. The gametophyte is subterranean and generally similar in form to some of the smaller sporophyte rhizomes. The sporophytes, along with those of the related Psilotum, lack true roots (making them almost unique among living vascular plants) and have instead rhizoids scattered on the underground stems. The spore bearing apparatus is unusual, consisting of a two-lobed synangium (of two fused sporangia) set in the angle between the two leaf-like lobes of the sporphyll. The normal leaves have a simple lamina, the fertile ones are two lobed. Until recently one widespread species - Tmesipteris tannensis - has been recognised in New Zealand, but Chinnock (1975) has shown that there are in fact four species, some of which are restricted to the northern part of the country. All species are to be found in the Auckland area. All may be found on the ground, but are most common as epiphytes on the trunks of tree ferns. Being relatively simple in form the differences are likewise simple differences in shape and arrangement of parts of the plant. Important differences are found in the shape of the synangia (spore bearing sacs), the distribution of the sporophylls (spore bearing leaves) on the plant, and in leaf shape and orientation. Thus it is important to look for fertile material. Key 2: Tmesipteris 1. Synangium pointed away from the sporophylls (Fig. Ia); leaves glossy, dark green. Sporophylls in one or more groups near the distal end of the frond T. tannensis (Spreng. ) Bernh Synangium pointed or blunt towards the sporophylls; leaves if glossy rather pale and broad. Sporophylls often in a single group either basal or distal 2 2. Sporophylls restricted to basal region (Fig. lc); leaves glossy, broad, pale green, conspicuously two ranked. (The frond flattened). Growth terminating in an enlarged terminal leaf T. lanceolata Dang. Sporophylls distal; leaves dull, narrow, not usually two ranked, growth indeterminate, the apparently terminal leaflet small and immature 3 3. Leaves arising all round stem, and long and slender in relation to stem, giving a delicate leafy appearance (Fig. Id); leaves long and narrow, more or less parallel sided, sigmoid bearing a long appendage arising from the truncate tip. Synangia 195 very small, blunt, widely gaping and splitting laterally when overmature and then easily deciduous T. sigmatifolia Chinnock Leaves arising all around stem but may appear flattened. Leaves not sigmoid, narrowing towards tip and with only a short appendage. Light, dull green in colour being distinctly less glossy than the other species. Sporophylls towards the tip of the frond, their laminae distinctly smaller than those of the vegetative leaves. Synangia slightly pointed toward the sporophylls and large in comparison with the sporophylls (Fig. Ib); gaping only slightly when spent, not splitting laterally and often retained on the plant T. elongata Dang. Notes on Tmesipteris T. tannensis. With its strikingly pointed synangia this species is easily distinguished when fertile, also it frequently has rather twisted leaves which are pointed, dark and glossy, giving an appearance unlike the other species - the only other glossy species (T. lanceolata) having short wide leaves in a complanate arrangement and basal sporophylls. T. tannensis fronds are usually fairly long. (T. lanceolata is always short. ) T. sigmatifolia. This species is rather less common than the others but is fairly easy to distinguish with its long sigmoid leaves very regularly spaced on the stem and the appendages which are quite strikingly elongate compared to the other species. When fertile the small blunt synangia which gape widely open when dehisced are also characteristic. T. elongata. This species occurs in two forms - the normal one being usually found on tree ferns, but a larger variety (var. robusta) usually occurring on other substrates such as the bases of Collospermum clumps.