Art. XLIV.—Notice of the Occurrence of Australian Orchids in New Zealand.
[Read before the Wellington Philosophical Society, 24th February, 1892.]
Caleana minor, R. Brown.
This remarkable plant was detected near Rotorua in 1890 by my friend the Rev. F. H. Spencer, who after protracted search succeeded in obtaining four or five specimens, which he generously presented to me. It is one of the most interesting additions to the New Zealand flora that have been made during recent years, and is, moreover, extremely rare outside the colony, having been observed only in two localities in New South Wales and another in Tasmania, occurring very sparingly in all its habitats. It was originally described by R. Brown in 1810. On account of the interest attending its discovery here, and for the convenience of New Zealand botanists, I append a somewhat detailed description.
Root of two or three short fibres and two small oblong tubers, which are irregularly narrowed towards their extremities. Stem and leaf glabrous, reddish; the former almost filiform, 4in.-6in. high: the leaf extremely narrow-linear, flat, from one-third to one-half the length of the stem. Flowers 1 to 3, on slender pedicels ¾in. long, with a small acute bract at the base, inverted: sepals and petals almost equal, about
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⅜in. long, linear, sometimes with infolded margins; the dorsal sepal narrow linear-spathulate, 3-nerved. The lateral sepals spring from either side of a strap-shaped process or hinge which carries the labellum, and is about 1/12in. long, and unequally waved or wrinkled at the margin. The labellum itself is broadly pear-shaped, but, owing to a constriction at the middle, is unequally 2-lobed: it is peltately attached by its broad end to the process just described, and is margined with rather large purplish-red tubercles, the largest being situate at the free extremity: the exterior surface is green. The column is nearly as long as the sepals, and is furnished with a large dilated wing on each side, the whole forming a cup-shaped cavity, which is capable of being closed by the labellum. Owing to the inversion of the flower, the anther occupies the lowest part. The entire flower presents a strange resemblance to a spider, the body of which is formed by the expanded and dilated column, the legs by the narrow-linear sepals and petals, and the cephalothorax by the labellum: the resemblance is increased by the dull-red or reddish-brown coloration of the column and the tips of both sepals and petals. The pollen-masses are four in number.
The position of the labellum when not closed is nearly horizontal, the free extremity being more or less ascending at first. One of my specimens has an apparently ripe capsule, with perfect seeds.
The following instructive and interesting remarks on the hinge of the labellum and on the probable mode of fertilisation in Caleana major, R. Br., are copied from the splendid work on “Australian Orchids” by R. D. Fitzgerald, F.L.S., and will be welcomed by all students of New Zealand plants: although the hinge is shorter in C. minor, there is no other difference:—
“The labellum is not sensitive, but when raised remains in unstable equilibrium, subject to be closed by a slight touch. The mechanism of the hinge by which this end is obtained is curious and simple. Imagine a thin strap of indiarubber having its edges slightly contracted: the result would be that the centre would bulge to one side or the other, and according to the side on which the convexity or concavity lay the strap would be bent. It is evident that a lid so supported would be ready to fall on a slight pressure from behind; but in this flower the column has taken the position usually occupied by the labellum, and an insect alighting on it would not bring down the lid, a touch or even a push from the front having no effect, while the falling of the lid from a touch on the back would be but to exclude the insect… It struck me that the weight of the insect might here act to bring down the labellum, which in other cases springs up by elasticity
against the weight. My first experiment was with a blow-fly, hung by a thread and let swing against the labellum. But the blow-flies were either too restive, or, by grasping the cup as well as the lid, prevented their weight from being felt by the labellum. I therefore had recourse to ladybirds as more tractable. One of the ladybirds which attack the Sola-nums was induced to climb up a match till it reached the end, when it readily left the wood for the labellum, and immediately the labellum descended and the insect was fairly caught in the cup. It remained imprisoned for about two minutes, when it forced itself out, but did not fertilise the flower or remove the pollen. Other ladybirds similarly entrapped escaped in from one to twenty minutes, but none of them fertilised the flower, the obvious reason being that they were caught with their backs to the column, and the breadth and smoothness of the back prevented the pollen or stigma from being touched. I had frequently placed Caleanas where house-flies would be likely to alight upon them, and had occasionally observed that they had closed the flowers, but the flies were never caught, and I believe the labellums were sprung by being struck from the back. To help nature and make the flowers more attractive in the proper part, I now placed a little honey on the front of the labellums of a dozen flowers, and was soon rewarded by the capture of several flies, only two of which, however, fertilised plants, and one perished in so doing—it was so firmly united to the stigma that it could not help itself. Six hours was the longest time noted as the imprisonment of a fly, but the labellum never rose until the insect escaped or (as in the one instance) died. The usual time for the flowers to remain shut when no insect is enclosed is from a quarter of an hour to an hour.”
Mr. Fitzgerald states that in all probability the right insects were not experimented with; and, whatever may be the cause, ripe capsules are very rarely produced.
It may be added that four species of Caleana have been described, all except C. minor being restricted to Australia.
Calochilus campestris, R. Brown.
Calochilus is a small genus comprising only three species, which until a few years back were supposed to be absolutely restricted to Australia. In 1882 Mr. J. Buchanan, F.L.S., reported the occurrence of C. paldosus in the Colling-wood district;* and in 1887 Mr. T. Ball showed me a single flower of another species collected by the late Mr. E. B. Dickson, B.A., in the Rotorua district; but it was not until 1890 that I was able to obtain good specimens, through the kind exertions of my old friend the Rev. F. H.
[Footnote] *Trans. N. Z. Inst., vol. xv., 340.
Spencer, who, although on the eve of leaving for England, gave himself considerable trouble in searching for the plant, and was rewarded with success. I am indebted solely to him for the opportunity of examining good specimens, which, although differing in one or two points from the Australian plant, must be identified with O. campestris, R. Br.
The specimens of this plant figured on t. 106A in Hooker's “Flora TasmaniÆ” represent a somewhat robust plant with a very short leaf, little more than a sheathing bract, several cauline bracts, and a short broad labellum, clothed with a red fringe on the margins and surface, except at the short beak-like point, which is naked. The Rotorua plant differs in having a long broad basal leaf, and one or two sheathing cauline bracts, and especially in the longer labellum, with its long naked flexuous tip, and the upper portion of the labellum clothed with large red calli. Mr. Fitzgerald's fine drawing in “Australian Orchids” represents the habit and structure of the New Zealand plant exactly, but differs in the coloration, the calli and fringes in all the Rotorua specimens seen by me being of a deep velvety red throughout, and showing no trace of blue or even of purple.
The Rotorua plant is usually robust, 9in. to 18in. high, with a leaf from one-third to two-thirds the length of the stem, ⅜in. to ⅝in. broad, and one or, less frequently, two sheathing cauline bracts. Flowers 3–6; pedicels, exceeded by the acuminate sheathing bracts, ½in.-1 ½in. long. Sepals 4–5 lines long, upper broadly ovate, almost galeate, lateral narrower, rather strongly veined; lateral petals shorter; labellum ⅝in.-¾in. long, terminating in a narrow flexuose naked tip, strongly fimbriate on the margins and upper surface for two-thirds of its length above, most of the upper portion being covered with rather large naked calli, which gradually pass into hairs on the expanded portion of the labellum; above the calli is a small naked bar which is slightly thickened. The column is furnished with two short broad wings reaching to slightly above the stigma, and broadly rounded in front, with a large intramarginal gland at the base of each wing; anther bent forward and projecting, so that the base of the pollen-masses projects beyond the rostrum, and comes in close contact with the stigma even before the flower is fully expanded, thus insuring self-fertilisation. Pollen-masses 2, clavate.