A New Species of Pachycladon

Transactions and Proceedings of the Royal Society of New Zealand, Volume 84, 1956-57, Page 497

A New Species of Pachycladon By W. R. Philipson [Received by the Editor, February 28, 1956.] Three alpine genera of Cruciferae in New Zealand possess a rather similar rosulate habit. Two of them, Notothlaspi and Pachycladon, are endemic to the South Island; the third, Cheesemania, while mainly centred in the Southern Alps, is represented in Tasmania by one species. In the vegetative condition, all the species of these genera consist of a stout fusiform root-stock crowned with a dense rosette of radical leaves. The leaves are spathulate or lanceolate, usually coarsely toothed or pinnatifid, and frequently bear simple or stellate hairs. Though so similar in vegetative characters, these three genera are readily separated by features of their fruits and seeds. The embryos of the species of Cheesemania are acumbent, whereas those of Notothlaspi and Pachycladon are incumbent. These last two genera may be distinguished by the valves of the fruits being broadly winged in the former and only faintly keeled in the latter. In 1953, when taking part in the Canterbury Museum Fiordland Expedition, I collected a small cruciferous plant from rock crevices at 5,000ft on the mountains west of Lake Te Au in the Murchison Range. The plants were very similar to Pachycladon novae-zelandiae in general appearance, but differed in possessing simple, not stellate hairs, and in the crenate, not pinnatifid, leaf margins. The fruit showed all the characters of Pachycladon and the embryo, when dissected out, was clearly incumbent. It was concluded, therefore, that a second species of the hitherto monotypic genus existed in Fiordland with a more southerly distribution than P. novae-zelandiae As the material was collected late in the season, when flowering material was not available, it was decided to defer description until the plant was completely known. A second expedition from the Canterbury Museum entered the area in the summer of 1954–55, when Mrs. M. Cookson kindly obtained for me material with abundant flowers from rocks on a ridge below the adjacent Coronation Peak. Pachycladon crenata n.sp. Herba perennis, rosulata. Folia ovata in petiolum attenuata, crenata. strigosa, 127 mm, petiolo circa 12 mm longo. Pedunculi arcuati, circa 5 cm longi. Flosculi 3–5, 6 mm longi. Fructus oblongo-lanceolatus, circa 12 × 0.5 mm, valvis leviter carinatibus. A small perennial herb with a tapering rootstock bearing a dense rosette of leaves. Blades of the radical leaves obovate, about 12 × 7 mm, coarsely crenate, bearing strigose hairs especially on the margins, obtuse at the apex, narrowed at the base into a broad flat petiole; the petiole as long as or longer than the blade. Cauline leaves few, smaller, cuneate or lanceolate, dentate. Peduncles many, axillary, arched-ascending, about 5 cm long, bearing about 3–5 flowers. Sepals equal, about 4 mm long. Petals obovate-spathulate, about 6 mm long. Stamens 4.5 mm long, anthers 0.75 mm long. Ovary ovoid, 3 mm long. Pod oblong-lanceolate, about 12 × 2.5 mm, valves obscurely keeled, septum perfect. Seeds about 10–12 in each loculus, funicles short. Cotyledons incumbent. Fiordland: Crevices on rock face at 5,000ft above source of Adams Burn, January 29, 1953, in fruit, W. R. Philipson (type in Canterbury Museum); rock crevice at 5,000ft on ridge running north-east from Coronation Peak, January 2, 1955, in flower, M. K. Cookson. I am indebted to Mr. C. M. Smith, Director of the Botany Division, D.S.I.R., for having the figure prepared by Miss N. M. Adams of his department. W. R.Philipson, B.A., Ph.D., Botany Department, Canterbury University College.

Pachycladon crenata, n.sp. A, plant in flower; B, plant in fruit; C, sepal; D, petal; E, stamen; F, gynoecium; G, fruit; H, septum showing attachment of seeds; I, embryo showing incumbent cotyledons; J, transverse section of seed. Magnifications: A—B × 4/5, C-F × 8, G-H × 5, I-J, × 30.

Fig. 2.—Geological Sections A-A′ and B-B′. Horizontal and vertical scales are the same, the legend is the same as for Fig. 1, and vertical ines represent offsets on the lines of section shown in Fig. 1. Fig. 1.—Geological Map of Southland. The geological sections are represented by solid linesand offsets shown by dashed lines.