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Volume 78, 1950
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4. Sarcochilus R. Br.

A genus of over 50 species, extending from India through Malaya to Australia, New Zealand, and Polynesia. Australia has 14 species, New Zealand only 1.

Sarcochilus adversus Hook, f., Flor. Nov. Zel., 1, 1853, 241. S. breviscapa Col., Trans. N.Z. Inst., 14, 1882, 332.

Epiphytic, usually confined to the upper branches of forest trees. Leaves 1–8, glabrous, coriaceous, up to 7 cm. long by 2 cm. broad, oblong ovate, acute or apiculate. Flowers 1–20 in a dense raceme rising from the axils of the lower leaves. As many as 5 peduncles are borne at a time. Stem and floral bracts minute, acuminate. Flowers minute, greenish-white, spotted with red. Sepals and petals more or less similar, the latter rather smaller, oblong acute. Labellum minute, coloured in a manner similar to the sepals, cup-shaped with 2 prominent greenish ealli near the tip. Column very small, rostellum prominent. Anther terminal, 2-celled. Column-wings dark purple, extending behind but not above the anther, and with acuminate lateral lobes forming a cavity over the stigma. Pollinia 4, 2 to each anthercell, attached to the rostellum by a caudicle. Pollen waxy.

Distribution. Endemic. Not uncommon throughout the North and South Islands, and extending to Stewart and the Chatham Islands.

Flowers October-November, sea-level-1,000 ft.

Pterostylis irsoniana Hh. n.sp.

Pt. montana typica et venosa affinis, probabilis hybridae originis.

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Map showing distribution of Pt. irsoniana Hh. Crosses mark the approximate spots where the colonies occur.

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Demlrobium cunninghamii: (a) leaf: (b) Flower from front; (c) labellum from front; (d) column and labellum from side; (e) column from side; (f) column from front; (g) showing typical form of bud.
Sarcochilus adversus: (h) plant natural size; (j) flower from front; (k) labellum from front (l) column from front; (m) column from side.

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Eirina mucronata: (a) raceme natural size; (b) flower from front; (e) flower from side; (d) labellum from above; (e) column from front; (f) column from side.

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Earina autumnalis: (a) raceme natural size; (b) flower from half front; (e) labellum from above; (d) column from front; (e) column from side.

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Bulbophyllum tubcrculatum: (a) plant reduced: (b) flower from side; (e) labellum from front: (d) column from side. Figs. a–d copied from the hypotype; after Smith.
Bulbophyllum pygmaenm: (e) leaf. pedunele, and flower. greatly enlarged; (f) plant natural size: (g) leaf and psendobulb; (h) labellum from side, showing elaw; (j) column from side.

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Pterostylis irsoniana: (a) plant natural size; (b) column and labellum from side; (c) labellum from above; (d) tip of labellum; (e) lateral sepals; (f) stigma; (g) juvenile.

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Folia montana similis, flos trullifolia alobula subsimilis. Sepalum dorsale caudatum, apex horizontalis aut incurvis. Sepala lateralia acuminata aut subulata, unum levis galea excedere. Labellum angustia gradatim ad apex levis turgidis, vel crenulata vel truncata. Basis labellum cum callo magno in genus singularis. Columna venosae typicae.

Up to 17 cm. high. Leaves 1–6, narrow- to broad-linear, acuminate, flat or repand, up to 8 cm. long by 12 mm. broad. Flower solitary, up to 16 mm. high, translucent, with green and red striae. Dorsal sepal shortly caudate, the tip incurved or horizontal. Lateral sepals with an acute sinus, the lobes acuminate or subulate, only slightly exceeding the galea. Petals rather broad, falcate, acute, shorter or longer than the dorsal sepal, the upper half conspicuously red. Labellum gradually narrowed to a slightly swollen, truncate or variously crenulate tip; more or less translucent with the raised midrib and the swollen tip a dark red. Base of the labellum with a large dark prominent callus which is unique in the genus so far as the writer is aware. Column typical of Pt. venosa.

Pt. irsoniana appears to have originated as a hybrid between Pt. montana typica Hh. and Pt. venosa Col. In its present state, however, it is obviously a true species, occurring over a wide area and breeding true to type. It produces ripe seed capsules, and undoubted seed-born juveniles of the montana type. Although the leaves vary considerably, the flower form remains constant. The general habit resembles that of montana. The flower is similar to trullifolia alobula except that the lateral sepals are usually acuminate as in montana. The column and labellum are those of venosa except that the latter has the swollen tip which is characteristic of trullifolia alobula. The basal callus cannot be likened to any known species of Pterostylis. This reversion to trullifolia is but further proof of the writer's contention that venosa has descended from the obtusa complex (Hatch, Trans. Roy. Soc. N.Z., 77, 1948, 243–4). In naming it, he has endeavoured to acknowledge the labours and enthusiasm of Messrs. J. B. Irwin and O. E. Gibson, who between them have done much to elucidate the orchid flora of Mount Egmont.

Distribution. Endemic; 6, Mount Egmont, 12.1947–8, O. E. Gibson, J. B. Irwin.

Flowers December–January, 3,000–4,000 ft. Locally abundant along grass tracks and roadsides and in scrub, in 6 or 7 localities on the northern and eastern slopes of Mount Egmont.

Holotype in Herb. Hatch. No. 568, North Egmont Hostel, 3,800 ft. 12.1948, O. E. Gibson. The accompanying illustration can be regarded as the hypotype of the species.

Mr. Gibson has had this plant under cultivation at New Plymouth since 1947, and reports that lowland conditions do not seem to affect the flower form at all, but that the leaves tend to be rather larger and the plant flowers a month earlier.

Except for Bulbophyllum tuberculatum, which was drawn up from the hypotype, the descriptions and illustrations in this paper have been prepared from living material examined by the writer.