Neville H.S. Howcroft
INTRODUCTION: Members of the genus are erect or climbing monopodial epiphytes and all bear terete leaves. The inflorescences are always short and elongate during flowering to produce several open flowers at a time. The labellum is fleshy, rigid and comprised of two parts, the basal part which may have cushion-like glands and very short sidelobes and the apical part which is usually somewhat ovate, sometimes with toothed margins. Usually the labellum is dark red and there is no spur at the base of the labellum.
Until recently the genus Luisia has been represented by only one species. This is Luisia teretifolia Gaud. This orchid, previously called Luisia beccarii, appears to be quite common in New Guinea. A second species has been found in the Papuan region and this appears to be an undescribed species. Its flowers are pale green with a green and maroon labellum whose apical margin is somewhat serrated.
In this paper the PNG L. teretifolia is represented by an illustration of a Markham Valley specimen which was collected from a felled Araucaria cunninghamii tree in 1975. A reproduction of the illustration of the type is also presented for comparison
DESCRIPTION: Luisia teretifolia Gaud. in Freyc.,Voy. Bot.:427, t.37(1826). Type: Mariana Islands, Guam, Gaudichaud 37(Holotype P.)
An epiphytic herb, erect to semi-pendulous, single stemmed or many branched, up to 70 cm tall. Leaves distichous, ridged, terete, 5 - 15 cm long, 2 - 5 mm in diameter. Inflorescences lateral, opposite leaf axil, 5 - 20 mm long, erect, thickened near apex with 1 - 3 flowers opening at a time. Flowers drooping, yellow to yellow green with wine red to maroon labellum, sometimes mottled, margin sometimes yellow or green, glabrous, 1 - 1.5 cm across. Dorsal sepal oblong, concave, 5- 7 mm long, 3-4 mm wide; lateral sepals concave obliquely ovate, slightly keeled, 7 - 8 mm long, 3 -4 mm wide; petals narrowly oblong, 1.5 - 2 mm long, 1.5 - 2 mm wide; labellum fleshy, 6 - 7 mm long , 6 - 7 mm wide, divided into two parts, concave in basal half with a circular, slightly raised pad-like gland in basal half, expanded into a fleshy cordate to sub- cordate apical blade, the lateral lobes are rudimentary (C). Column about 4 mm long with a short column foot 2 mm long.
View drawing: Luisia teretifolia Gaud.
drawing by Neville H.S. Howcroft
Key to illustration: A - plant habit (5 cm scale), B - flower (10 mm scale), C - cut away view of flower (10 mm scale), D - petal, E - lateral sepal, F - labellum flattened (all to 10 mm scale)
DISTRIBUTION: Widely distributed from S.E. Asia to Malaya peninsula, throughout New Guinea, to Vanuatu, the Mariana Islands, New Caledonia and Australia.
HABITAT: Paperbark and Gallery forests on the Papuan side of New Guinea to montane forests in the mountains. Rainforest situations and on secondary regrowth trees. Altitudinal range is from sealevel to c. 1,500 m above sea level.
The species described here appears to be fairly common on planted trees around the town areas such as Alotau, Lae, Bulolo, Wau, Finschhafen and Madang. The most common host tree in these towns is the Rain Tree (Samanea saman).
NOTES: Schlechter (1914) comments that there is a need to revise this genus and Seidenfaden (1971) attempted to do this recognising some 36 species but also noted further taxonomic confusion with several taxa.
Based on observations of live specimens from the Arfak mountains in Irian Jaya, and from Bulolo and the Central province region, it is obvious that there is still a need to examine the New Guinea Luisia teretifolia more critically as some specimens bear two glands in the basal part of the labellum while other have only one. The flowers look identical in size, shape and colour.
The Markham specimen has only one gland in the basal half of the labellum as I have attempted to show in the illustration, keys F and B. This gland also shows up in the cross section of the flower, just at the base of the column and directly below the stigma.
Seidenfaden (1971) makes mention of a L. macrocarpa Schlechter from New Guinea, as I have not seen the protologue for this so I cannot compare it here. Further, Seidenfaden suggests that students collecting fresh material from New Guinea and the Pacific Islands may find that they are different from the Guam species. He further suggests that possibly L. beccarii could be maintained as a species separate from L. teretifolia.
CULTIVATION: Extremely easy to introduce to garden trees and shrubs and it will grow well in pots filled with broken crocks and gravel or in baskets. It requires good drainage and will tolerate semi-shade to exposed situations.
Raulerson and Rinehart (1992) mention that L. teretifolia has been successfully crossed with Vanda x Miss Joaquim. The registered hybrid is called x Uniwai.
CONSERVATION STATUS: The species is common and wide spread as well as being associated with many forest types, it is also common among urban vegetation thereby ensuring seed sources. Allowing for losses, due to commercial logging and agricultural development, the species survival chances are very good and there appears to be no need to recommend that it be protected.
REFERENCES:
Lewis, B.A. & Cribb, P.J. 1991, Orchids of the Solomon Islands and Bougainville Kew .335
Raulerson, L. & Rinehart, A.F. 1992. Ferns and orchids of The Mariana Islands. 138
Schlechter, R.(1911-14) Die Orchidaceen von Deutsch-Neu-Guinea. Fedde, Repert. Spec. Nov.Regni Veg., Beih. 1:-1079
Seidenfaden, G. 1971. Notes on The Genus Luisia. Dansk Botanisk Arkiv27(4): 1-101
