Journal Number 89
December 2003

EDITORIAL

Nematoceras iridescens in the Far South
By Ian St George

Kelley Rennell's recent discoveries of a plant in the Nematoceras rivularis complex in Southland prompts me to remind readers of the plants near Dunedin regarded as a dysjunct population of N. iridescens, discussed in my Nature guide, and illustrated on the cover of J60.

The flower is lighter coloured than some North Is forms, and brownish in Otago. The dorsal sepal is greenish with raised brown streaks. The labellum is very sharply deflexed, flaring widely; it sometimes lacks the beadlike callus at the entrance to the column cavity.

In Otago the leaf emerges from the ground in November as a tight cone, which widens to reveal
the immature flower, its petals and sepals curled above the other parts. As the flower matures,
the leaf flattens and the sepals and petals straighten. It likes wet areas, and can often be found
in running water.

I have seen it in the Leith Valley, Trotters Gorge, and Berwick Forest nature reserve near Dunedin.

The High Schools teacher and botanist (later politician) G.M. Thomson noted in his diary (in the Hocken Library) in 1879, "Corysanthes: the species found on stones in Nicholl's creek - now fast disappearing - may be either C. rivularis or C. macrantha. Like so many other plants they probably run into one another".

This was N. iridescens and his difficulty in separating it from N. macranthus indicates that he understood the similarity (both species have round leaves), and was not, as the northern botanists, confused with N. acuminatus.

The surveyor John Buchanan who arrived in Otago in 1852 and sent back to Kew what J.D. Hooker described as the best collections of plants received from Australasia, explored much of the interior, often in the company of Dr Hector. The Hocken Library has a number of his diaries, and they give a vivid picture of the hardships of collecting.

He was a prolific artist. Sketchbooks in Dunedin, Wellington and Auckland are full of beautiful natural history and topographical drawings. He was chief illustrator for the Transactions of the New Zealand Institute, and drew and engraved many of the lithographs for its first nineteen volumes - "JB del." appears on most. His "Milford Sound, looking North-West from Freshwater Basin" has been described as one of the masterpieces of New Zealand landscape painting.

One of his sketchbooks in the Alexander Turnbull Library contains copies of the W.H. Fitch
lithographs of New Zealand orchids; in the Transactions is also a lithograph of a plant he
collected near Picton and called Gastrodia hectori - it was identified by Cheeseman as
Prasophyllum aff. patens, and the specific epithet is likely to be applied to one of the taxa of
this undescribed aggregate.

In one of the sketchbooks in Dunedin is a watercolour dated 25 November 1862 and labelled
"wet banks of creek under shade of trees, North side, North East Valley. Nematoceras (?triloba)".
It is Nematoceras iridescens. (See Below).

Or is it? It has some subtle differences from many North Is plants, and the population is distant and isolated (dysjunct) from the otherwise southernmost plants I know of, near Levin. Has anyone seen it in the intervening territory?

Bruce Irwin thinks it is N. iridescens; 25 years ago he saw many plants resembling this on
Stewart Is, and on 18 Oct 90 he drew a specimen I sent him from Leith Valley.

 Nematoceras iridescens
 Watercolour by John Buchanan, 25 Nov 1862
"Wet banks of creek under shade of trees, Northside, North East Valley".