A New Species of Corybas Salisbury, and a Note on Some
Name Changes in Wahlenbergia Schrader
[Read before the Auckland Institute, September 6, 1950; received by the Editor, September 25, 1950]
Two subterranean orchid genera (Rhizanthella Rog. and Cryptanthemis Rupp.) occur in Australia. Both consist of a tuberless, leafless, branching rhizome which bears terminal capita, and flowers beneath the surface of the soil.
The new species described here is not strictly subterranean, for the rhizome lies on the surface, but it is subterranean in effect, for rhizome, leaf and flower are all buried beneath the surface debris. And in common with the Australian plants, Corybas saprophyticus is a tuberless, almost leafless, branching rhizome bearing terminal flowers. It seems that these characteristics are the result of a particular environment rather than specific or generic differences.
Corybas saprophyticus Hh. n.sp. Plate 71
Corybas rivularis affinis, saprophyticus, semi-subterraneus. Caulis plantae horizontalis, ramosus, nulli tuberis. Folium minimum, terminale, non viride. Flos in proportio magnus et totus substratum debris. Sepalum dorsale erectum, acuminatum. Sepala lateralia et petala filiformi-caudata. Labellum ad basim tubulum, auriculis. Discus orbiculatus fimbriis ad margino. Columna rivularis similis, differentis in alae columnae maxima. Peduncula elongata capsula matura et spectabilis super terra.
A saprophytic, almost subterranean species allied to C. rivularis (A. Cunn.) Reichb. f. Mature plant body a perennial, horizontal rhizome without tubers, creeping on the surface of the soil but entirely out of sight beneath the debris of twigs, leaves, mould and moss. Rhizome slender, whitish, with scale bracts at the nodes and the internodes sparsely seattered with short rootlets. Branches arising from the axils of the scale bracts. Leaves solitary, terminal on the branches, whitish with red flecks, oblong-acute or -apiculate, up to 1 cm. long by 4 mm. broad. Floral bract rudimentary, minute. Secondary bract wanting. Flowers solitary, sessile on the leaf, translucent with red flecks and fimbriae, up to 25 mm. high, and completely buried under the surface debris. Dorsal sepal erect, concave, acuminate. Lateral sepals filiform-caudate, erect or spreading. Petals similar, about a third as long. Labellum tubular at the base with prominent open auricles. Disc expanded, orbicular, the margins more or less upturned, with irregular red fimbriae. Column as in C. rivularis, but differing in the prominent column-wings being continued behind and above the anther. Seeding peduncle elongating to 15 cm. high. This is the only part of the plant normally visible and is conspicuous by the bright red flecks and the absence of a leaf.
A. Corybas saprophyticus Hh., natural size.
B. Seeding stage, reduced.
C. Labellum from above.
D. Column from above.
E. Column from side.
F. Column from front.
G. Column from side, anther and column-wings removed to show stigma and rostellum.
H. Lateral sepal at immature bud stage, showing concave formation.
J. Immature bud stage, showing leaf enclosing the flower.
Distribution: Endemic—3a. Wellsford, 25.10.1949 (seeding stage), Irwin and Gibson. 5.6.1950 (immature buds), Bartlett, Irwin and Hatch. 29.7.1950 (full flower), Hatch and Bartlett. 6. Waitotara, 12.1949 (seeding stage), J. B. Irwin.
Holotype in Herb. Hatch, No. 569 Wellsford, 29.7.1950, E. D. Hatch. The accompanying illustration can be regarded as the hypotype of the species.
Tendencies. Although C. aconitiflorus Salisb. belongs to a different section of the genus, it will serve to show how several evolutionary tendencies have been carried to their logical conclusion in the new species. In C. aconitiflorus the stem is often horizontal and consequently buried, the leaf frequently very small and the flower barely manages to struggle through the surface debris. In C. saprophyticus the stem is always horizontal and completely buried. The leaf has lost its chlorophyll, taken over the function of the floral bract and given up trying to break through to the light. The true floral bract has become a mere vestige and the secondary bract which is normal in most Corybas species (but not in C. aconitiflorus) has disappeared entirely.
One interesting result of the study of the immature bud was the basic nature of the filiform sepals and petals. In full flower, even under the microscope, these appear to be quite solid, but in the very early stages they are clearly narrow-linear concave blades with distinctly serrated margins.
Reproduction. C. saprophyticus is almost certainly self-fertile and all the flowers normally set seed. The large column-wings are designed in a manner similar to those of Thelymitra pachyphylla Cheesmn. (a species notorious for cleistogamy) and the falling pollinia have only one way out—across the face of the stigma. The purpose of the tuber in most Corybas species is (a) to tide the plant over the dormant season and (b) to provide a means of vegetative reproduction. In C. saprophyticus the rhizome is truly perennial, and does away with the necessity for (a). Vegetative reproduction is effected by the rhizome growing and branching ahead and dying away behind. Whenever the point of dissolution reaches a fork the branch becomes separated from the parent body. Since the growth of the branches is indefinite, each branch thus separated becomes an independent plant. Factors (a) and (b) having been eliminated, the tuber becomes superfluous and disappears. Gibson had the Waitotara rhizomes under cultivation at New Plymouth and reported that under the stimulus of the artificial environment, mature plants did form tubers before dying out. The writer observed a similar reaction in Pterostylis trullifolia Hook. f. (Trans. R.S.N.Z., 77, 1949, 245). It is possible that tubers would be formed in nature whenever adverse circumstances caused the rhizome to die ont gradually. Irwin's notes on the original colony of seeding plants record that they were arranged in a circle, as though they had radiated out from a common centre. This suggests vegetative reproduction. The odd plants found scattered over the ridge by Bartlett and the writer were more probably from seed.
Development. Protocorms of an oblongus type were found in the moss surrounding C. saprophyticus. C. oblongus was in the area although not in the immediate vicinity, and the protocorms could have belonged to this species. If, however, as the writer suspects, these protocorms were from C. saprophyticus, then development would be along the following lines:
The seed develops through the protocorm to the minute 2-leaved stage, when a tiny tuber is formed. Then instead of producing a single-leaved miniature of the adult as in C. oblongus, this tuber develops into a minute rhizome, which being perennial, grows ahead and thickens until it becomes sufficiently robust to begin branching. At this stage flower buds are formed. The specimens discovered at Wellsford had from 2–6 branches and up to 4 flower buds. There was no sign of secondary branching and it seems probable that a lateral shoot does not begin to branch until it becomes separated from the parent rhizome. After fertilisation the capsule is raised above the surface by elongation of the peduncle between the leaf and the floral bract, which process leaves the leaf out of sight below the surface debris.
Nutrition. In the complete absence of chlorophyll, nutrition must be by means of mycorrhiza or bacteria or both, and it is probable that the rootlets only serve to take in water. There is a great deal of organic matter in the debris layer and fungal hyphae abound
Ecology. Waitotara—Nothofagus forest with little undergrowth. C. saprophyticus was found under clumps of moss among a colony of C. trilobus. Wellsford—a horseshoe-shaped ridge enclosing a small valley facing east. Mature, rather open, manuka scrub dominated by Leptospermum scoparium, and containing the association usual in incipient Podocarp-Kauri forest. Undergrowth badly chewed about by cattle. Ground cover dominated by large clumps of a species of the moss Leucobryum. C. saprophyticus was found both under these clumps and under the twig debris where the manuka was more compact. Other orchids recorded from the area were:
Thelymitra longifolia Forst., Th. pauciflora R. Br., Pterostylis trullifolia var. gracilis Cheesmn., Pt. barbata Ldl., Acianthus forncicatus var. sinclairi (Hook. f.) Hh., A. reniformis var. oblongus (Hook. f.), Rupp and Hh., Caladenia carnea var. minor (Hook. f.) Hh., Earina mucronata Ldl., Prasophyllum pumilum Hook. f., Corybas trilobus (Hook. f.) Reichb. f., C. oblongus (Hook. f.) Reichb. f.
Notes on Some Name Changes in
In Proc. Linn. Soc. N.S.W., 71, 1947, 201 et seq., T. R. N. Lothian revised the Australian and New Caledonian species of Wahlenbergia. Lothian's work only affected one of our New Zealand species—the W. “gracilis” of Cheeseman.
Campanula marginata Thunb., Flor. Jap., 1784, 89, antedates Campanula gracilis Forst. f., Flor. Ins. Austr. Prodr., 1786, 84, and the valid name of the species is therefore:
Wahlenbergia marginata (Thunb.) AD.C., Monogr. Camp., 1830, 142
W. marginata, in the broad sense, consists of at least five jordanons, one in Japan and China (Campanula marginata Thunb.); one in Java (Campanula lavendulaefolia Rein.); two in New Caledonia (Campanula gracilis Forst. f. and Wahlenbergia marginata var. neocaledonica Loth.); and one in New Zealand. Both Lothian and the writer consider this latter plant to be allied to but distinct from the New Caledonian “gracilis” jordanon and suggest for it the name:
Wahlenbergia marginata var. australis Hh. n.nom.
Syn. W. gracilis Cheesmn. and others (not of Forst. f.).
Since it is probable that more than one jordanon of this species occurs in New Zealand, it is as well to define var. australis as the common blue-flowered plant which is to be found about Auckland, Wellington and New Plymouth. The type locality is Laingholm and type material has been deposited in the Auckland Museum.
The writer is extremely grateful to Messrs. J. B. Irwin, O. E. Gibson, F. W. Bartlett, and Robert Cooper for assistance with the Corybas, and T. R. N. Lothian, Robert Cooper, and F. W. Bartlett for further help with Wahlenbergia.