Journal Number 95
May 2005

ORIGINAL PAPERS

Pterostylis humilis R.S.Rogers: An Orchid With A Past
By ED Hatch, Laingholm - Reprinted from NZNOG Journal 55:11

I first found Pterostylis humilis in the autumn, in April, when the large leaves were turning bright yellow and were most conspicuous. The plants were of course in seed. I had no idea what they were and they didn't seem to be listed in Cheeseman's 1925 Manual. (I did not in fact discover the identity of this plant until May 1944, when I was in Dunedin, and Dr Ella Campbell gave me a copy of Rogers' paper.)

They were growing in the shelter of Hebe odora, on the edge of one of those pumice stacks, which in pre-bulldozer days, were such a feature of the Rangipo Desert.

In 1942 there were several Nothofagus copses on the southeast side of Ruapehu, at about
1200m asl, containing a number of orchid species which I duly noted and examined -
Chiloglottis cornuta, Corybas trilobus, Gastrodia cunninghamii, Pterostylis montana,
P. patens and what I later learned was P. humilis. Most of these grew inside the copses, in
the relative calm of the low forest, but P. humilis grew round the margins, exposed and out
in the open.

I had never before seen an orchid actually flowering in the snow, and wondered how the plant managed to survive in that harsh sub-alpine environment. Tracing one plant down through the scree, I found that the relatively large tubers were 150mm below the surface. Pile a metre or so of snow on top of that and humilis would be as happy as a hibernating bear. The tubers had to be large, in order to store enough nourishment to enable the rhizome to reach the surface. I'm still a bit puzzled though, to know how the seed manages to germinate under such conditions.

The plants were obviously self-pollinated. The column was erect, so that the anther was directly above the stigma. The pollinia were extremely sensitive, the slightest touch to the flower being sufficient to cause them to fall. The stigma was globose and relatively large, protruding forward beyond the vertical line of the anther. The lower lobes of the column-wings were strongly incurved and almost touching the stigma - so that the falling pollinium was caught between them and the viscid stigmatic cells.

(In passing, P. montana was similarly self-pollinated, while P. patens, though growing under the same conditions, but with a different column structure, was not).

P. humilis does not always grow in such bleak places, and I found it later on the Ohakune Track, on the forested west side of the mountain; far away to the east on the Kaimanawa Ranges; and of course on Mt Egmont, where it grows under subalpine scrub.
 

The history of Pterostylis humilis

In January 1921 H.B. Matthews found seeding plants "near the Haunted Whare, Waimarino". (The shepherd's hut which used to stand beside the Tawhai Falls, on State Highway 48 - the road up to the Chateau Tongariro). Matthews dug up the plants, pressed the specimens, and took the tubers back with him to Auckland, where he planted them out in a wooden seed tray.

By 23 October 1921 these tubers had produced stunted plants with malformed flowers, nothing like the species as it grew in the mountains. Matthews nevertheless pickled the plants in spirit and sent them off to Dr Rogers in Adelaide, along with a photograph showing one of them beside one of the original pressed seeding specimens. Rogers described Pterostylis humilis from the stunted spirit specimens, at the same time mentioning the photograph of the large-leaved plant.

In 1944 I asked Dr H.H. Allan to compare P. humilis from Ruapehu, with his P. confertifolia from the Ruahines. He replied that they were identical. Unfortunately he was wrong.

P. confertifolia was in fact a synonym of Colenso's P. venosa, as was later pointed out by
A.P. Druce. But who was I to argue with H.H. Allan? I had never seen the type specimens of
either confertifolia or venosa, nor could I gain access to them, and P. venosa, (like
P. irsoniana), while common enough on Egmont, was unfortunately  absent from Ruapehu,
so that I could not compare living material.

In 1945 I chose one of Matthews' original seeding specimens to be the Lectotype of
P. humilis (AK 108491 C).