7. Epipremnum pinnatum 'Aureum'
Epipremnum pinnatum (L.) Engl. 'Aureum' (see Nicolson, Allertonia 1 (1978) 347.) -- Pothos aureus Linden & André, Ill. Hort. 27 (1880) 69. -- Scindapsus aureus (Linden & André) Engl. in Engl., Pflanzenr. 37 (IV.23B) (1908) 80. -- Rhaphidophora aurea (Linden & André) Birdsey, Baileya 10 (1963, ‘1962’) 159 -- [Rhaphidophora aurea (Linden & André) Furtado, Gard. Bull. Singapore 20 (1964) 379, comb. superfl.] Epipemnum aureum (Linden & André) G.S. Bunting, Ann. Missouri Bot. Gard. 50 (1964, ‘1963’) 28. -- Type: Ill. Hort. 27 (1880) pl. 381. Epipremnum mooreense Nadeaud, J. de Botanique 13 (1899): 6. Type: ****, Nadeaud s.n. (P holo!)

Very large root-climber to 16 m. Pre-adult plant usually forming modest terrestrial colonies. Adult plant with stem 5--40 mm diam., internodes 2--30 cm long, separated by prominent leaf scars, with prominent irregular whitish longitudinal crests, older stems with distinctive matt to sub-lustrous orange-brown papery epidermis growing stems mid-green to pale yellow-green, occasionally with obscure large dull yellow to white variegations. Flagellate foraging shoots common, these arising high in the canopy and reaching the ground. Aerial roots of two types, clasping roots densely arising from nodes and internodes, feeding roots prolific, both strongly adherent to substrate and free, both root types pubescent, mid- to dark brown, growing tip pale brown-yellow, feeding roots later prominently lenticellate. Cataphylls and prophylls soon drying and then degrading to netted sheaths, these sparsely clothing upper stem and mostly soon falling. Foliage leaves scattered on lower stem, becoming clustered distally. Petiole 19.5--50 cm x 3--15 mm, canaliculate, smooth, mid-green to rather bright yellow-green, air-drying mid- to dark brown; apical geniculum 16--50 x 3--8 mm, smooth, basal geniculum 3--7 x 1--1.5 cm, both genicula barely on not greater in diameter than petiole; petiolar sheath extending to up to mid-way along apical geniculum, at first sub-membranaceous, soon drying chartaceous and degrading to untidy, slightly netted weak fibres, then falling to leave a smooth, mid-brown scar. Lamina 10--93 x 5--60 cm, entire to irregularly pinnatifid, ovate to elliptic in outline, sub-coriaceous, apex acute to acuminate, base moderately cordate, divisions pinnatifid to pinnatipartite; pinnae up to half the length of the lamina wide, apex truncate; terminal pinna, if present, smooth-margined, some leaves with few minute pellucid dots adjacent to the midrib in leaves, pellucid dots rarely perforating and almost never enlarging, lamina dull to somewhat glossy mid-green; slightly paler beneath, usually irregularly yellow or white variegated, rarely entirely mid-green; pinnae each with 1 (very rarely more except for the terminal pinna) compound primary lateral vein and several to rather many interprimary veins, these diverging from midrib at c. 70°, individual elements of the compound vein diverging at c. 10° from various points along the pinna, the vein thus becoming finer towards the margin; interprimary and secondary venation mostly remaining sub-parallel to compound primary vein, some weaker elements further dividing and becoming sub-reticulate, all other higher order venation conspicuously reticulate, midrib impressed above, very prominently raised beneath, lower order venation slightly impressed to almost flush above, variously raised beneath, higher order venation flush above, flush or nearly so beneath in fresh material but raised and rather conspicuous in dried specimens. Inflorescences several together, first inflorescence subtended by a usually fully developed foliage leaf and a swiftly disintegrating cataphyll, at anthesis partially to almost completely exposed. Peduncle c. 6 cm x 10--15 mm, stout, terete, pale green to yellow-green. Spathe canoe-shaped, shortly acuminate, spreading wide at anthesis and margins reflexing, c. 15 cm x 6--7 cm when pressed flat, exterior green, later whitish, interior whitish, air-drying dark brown. Spadix 17--19 x 2--3 cm, sessile, cylindrical, bluntly tapering towards the apex, base slightly obliquely inserted, whitish, air-drying almost black. Flowers 3--5 mm diam.; ovary 4--6 x 3--5 mm, cylindrical, basal part slightly compressed; ovules 2 ; stylar region 3--5 x 2.5--5.5 mm, trapezoid, rather robust, apex flattened, margins somewhat raised in dry material; stigma linear, 2--6 x 0.1--0.5 mm, longitudinal; stamens 4; filaments c. 6 x 0.5 mm; anthers narrowly ellipsoid, c. 1.5 x 0.75--1 mm;.

Distribution - Unknown in the wild, alleged to have originated in the Solomon Islands.

Habitat - Unknown in the wild. Where it escapes in Malaysia it grows in damp evergreen forest and abandoned rubber plantations at low altitudes.

Note - 1. Described from cultivated material alleged to have originated in the Solomon Islands, E. pinnatum 'Aureum' has a tortuous nomenclatural history. It was first published as Pothos aureus (Linden & André 1880) based on sterile pre-adult material. The curious choice of generic placement, given the manifestly different appearance of the plant to any species of Pothos as then circumscribed, remained unchallenged until Engler (Engler & Krause, 1908) removed the species, still unflowered, to Scindapsus. His generic choice was influenced by the plants’ overall appearance. There it remained until Birdsey (1962) reported the first recorded flowerings, in Puerto Rico and at the Fairchild Tropical Garden, Florida, and thus for the first time the critical ovule characters that showed the plant to belong to Epipremnum sensu Engler & Krause (1908). However, Birdsey chose to follow Bakhuizen’s (1958) generic ideas and transferred Pothos aureus to Rhaphidophora as R. aurea. Furtado (1964), unaware of Birdsey’s publication, published the same combination when reporting the flowering of "P. aurea" in Singapore. Furtado based his generic placement upon D.H. Nicolson’s hand-written annotations to Engler & Krause’s (1908) key (Nicolson then also followed Bakhuizen’s generic concepts). Bunting (1964), transferring P. aureus to Epipremnum, remarked that ‘flowering material is very similar to that of E. pinnatum, and must be included in that genus’. He went on to reiterate the characters he regardd as distinct for Epipremnum compared with Rhaphidophora. Nicolson’s (1978) paper discussing E. aureum and E. pinnatum stated that there were insufficient differences for them to remain distinct species and concluded by proposing that E. aureum be regarded as cultivar of E. pinnatum. In the same paper Nicolson also laid to rest the long-standing nomenclatural problems associated with the names Epipremnum and Rhaphidophora that formed the cornerstone of Bakhuizen’s paper (Bakhuizen, 1958). Nicolson’s 1978 generic circumscription and cultivar status of ‘aureum’ have since been incorporated into floras of Fiji and Sri Lanka (Nicolson 1979, 1988) and various checklists (e.g. Hay et al., 1995).
2. The wild provenance of 'Aureum' is unresolved. The type description of Pothos aureus states that the original plant came to Linden’s garden from the Solomon Islands, but this cannot be substantiated. Certainly 'Aureum' appears never to have been collected in the wild and the possibility exists that it is a horticultural selection of E. pinnatum. Such selections, looking radically different to the progenitor, are common in some plants (Codiaeum, Polyscias, etc.) and when seen in isolation appear highly distinct. Plant hunters of the nineteenth century were often on the look out for new horticultural novelties and it is possible that 'Aureum' was gathered from cultivation somewhere in the Solomon Islands.
3. There exists a suite of vegetative characters that consistently separate E. pinnatum and 'Aureum'. Based on observations made in Zone 1 of the Tropical Conservatory at Kew, at the Forest Research Institute Malaysia, Kepong and in Bogor Botanic Garden, Java the following can be stated. Beginning at the earliest observed stage, that of young pre-adult plants, the leaf laminae are different in shape and texture. Those of 'Aureum' are ovate to ovate-lanceolate and thicker in texture than the lanceolate to elliptic pre-adult leaves typical of E. pinnatum. As plants progress through the pre-adult stage and approach maturity more differences become apparent. The distinctive netted sheath-remains usually present in E. pinnatum are absent in 'Aureum' while the leaf lamina ‘pin-holes’ characteristic of E. pinnatum are far fewer in number, do not develop to any degree and hardly ever perforate. Leaf division by means of pinnation is sporadic and occurs only as solitary to few irregular rather shallow pinnations. Leaf texture remains consistently thicker than for E. pinnatum and leaf lamina shape remains more-or-less constant, the lamina simply increasing in size and not perceptibly altering shape. Massive flagellate foraging shoots develop, often in some quantity, and a profusion of prominently lenticellate robust feeding roots is produced, many of which remain hanging free and reach the ground. Overall the plants are considerably more robust and produce many climbing stems (E. pinnatum is generally noticeably less robust and few-stemmed). The observations made at the Forest Research Institute Malaysia, Kepong and Bogor Botanic Garden, Java support those at Kew. All the characters observed at Kew were seen in large numbers of plants of both E. pinnatum and 'Aureum' growing in a variety of situations. Most notably, several plants of 'Aureum' with entirely green leaf laminae were observed that retained the distinctive overall appearance of the variegated plants. Furtado’s comment that the variegated plant ‘reverts’ to the typical green plant in shady situations was not supported by my observations in Bogor where mature variegated plants were often seen in deep shade and adult green plants could be seen in full sun. This suggests that the green forms are somatic segregates from the variegated chimera. Most literature emphasises the shy-flowering nature of 'Aureum'. Enquiries at Bogor confirmed that both the variegated and the wholly green plants of 'Aureum' cultivated there are shy-flowering. This is in marked contrast to E. pinnatum which flowers profusely wherever it occurs in the wild and in cultivation.