Art. LV.—Description of a New Species of Chenopodium—C. buchanani.
[Read before the Wettington Philosophical Society, 12th June, 1889.]
This remarkable plant was discovered so far back as 1868 by Mr. J. Buchanan in Port Nicholson, where it is restricted to a single habitat. In the absence of female flowers it was doubtfully referred to C. triandrum, Forster, and subsequently to C. pusillum, Hook. f. About eight or nine years ago I received specimens of the same plant from Mr. D. Petrie, who collected them on the Maniototo Plains; subsequently I had the good fortune to discover the plant in two other localities: but until recently the female flowers remained undetected. It is usually restricted to a very limited area in each locality, and occurs in situations where it is exposed to the influence of the sea-spray; but to both these peculiarities there is a notable exception, which requires special mention. On the Maniototo Plains I found it growing at a distance of eighty miles from the sea and an elevation of 1,800ft., extending in vast profusion for many miles, although with occasional breaks, its habitat being a whitish clay strongly impregnated with saline matter. Wherever this bed is exposed the Chenopodium is abundant, associated with other plants usually restricted to littoral situations.
This species forms depressed white or greyish patches, which are easily recognized at a considerable distance owing to the mealy tomentum with which the plant is covered. The stems are excessively branched, the branches being stiff and wiry, especially when dry. The flowers are extremely minute: the female, being much smaller than the male, are necessarily inconspicuous; but this is not the only cause of their having escaped notice so long: the female perianth is developed on the lower parts of the branches; it is of the same consistence as the farinose leaves, and so closely resembles the tip of an impoverished branchlet springing from the axil of a leaf that its true nature is only shown by the extremely minute stigmas, which, being extremely delicate and fragile, are easily overlooked, even by a good observer. All traces of the stigma disappear in badly-dried specimens, and it is not an easy matter to detect the female flowers on good specimens, even when they are freely developed. The yellow anthers of the male flowers, which are produced near the tips of the branches, attract attention even on a cursory examination.
It affords me great pleasure to connect the name of its original discover, Mr. J. Buchanan, F.L.S., with this interesting species.
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An annual monœcious herb clothed with farinose tomentum. Stems prostrate or sub-erect, lin.–Sin. high, excessively branched, branches wiry. Leaves opposite or alternate, sessile or sub-sessile, ⅛in.–¼in. long, entire, ovate, or ovate-oblong, or nearly orbicular. Flowers axillary, solitary—male, near the tips of the branches, perianth membranous, shortly peduncled, minutely papillose, 5-cleft, tips of segments incurved, stamens 5, exserted; female, on the lower parts of the branches, 1/20in. long, sessile, perianth urceolate, farinose, 2-lipped, stigmas 2. Seed rounded, much compressed, puncticulate, adhering to the utricle.
Hab. New Zealand. North Island: Port Nicholson; J. Buchanan, T. Kirk. South Island: The Brothers Rocks, Nelson; C. Robson! Maniototo Plains (1,800ft.); D. Petrie, T. Kirk. Centre Island, Foveaux Strait; T. Kirk.
Description of Plate XXXII.
Fig. 1. Young plant, natural size.
Fig. 2. Staminate flower, natural size and enlarged.
Fig. 3. Pistillate flower, natural size and enlarged.
Fig. 4. Pistil, slightly enlarged.
Fig. 5. Seed, natural size and enlarged.
Fig. 6. " side view, enlarged.