Art. III.—A Description of a Species of Orobanche (supposed to be new) parasitical on a Plant of Hydrocotyle.

Transactions and Proceedings of the Royal Society of New Zealand, Volume 21, 1888, Page 41

Art. III.—A Description of a Species of Orobanche (supposed to be new) parasitical on a Plant of Hydrocotyle. By William Colenso, F.R.S., F.L.S., &c. [Read before the Hawke's Bay Philosophical Institute, 12th November, 1888.] Orobanche hydrocotylei, Col. Plant erect, simple, 12in.–18in. high, cylindrical, rather stout, as thick at base as a large-size common lead-pencil, darkish purple-red; whole plant thickly glandular-pubescent; hairs short, patent, whitish, their globular tips yellow. Bracts scattered, few at base, very distant below on stem, ¾in.–1in.

apart, and (with flowers) mostly running in three lines; ovateacuminate, dark-purple, many veined; tips recurved. Flowers 20–40, loosely spiked on upper two-thirds of stem, distant throughout ½in.–¾in. apart, presenting a sub-decussate appearance, sessile; floral bract as long as corolla. Calyx beneath only (corolla naked at top and sides), purple, ovate-acuminate, 2-leaved, each bilobed nearly to base; lobes long acuminate, unequal, the outer lobe twice the length of the inner one and half as long as corolla, sub-erect, divergent, their margins slightly and finely sub-denticulate and much ciliate. Corolla sub-ascending, patent, arched, 7–8 lines long, cylindrical, mouth broadly dilated, margins recurved; the upper half purple above; base and sides white; veins darkpurple; lips whitish dashed with purple, their margins irregularly denticulate or laciniate-toothed, wavy; glabrous within, shining; the upper lip projecting beyond the lower one, deeply emarginate or sub-bilobed, lobes rounded, sometimes slightly decurved; the lower lip larger, much recurved, sub-3-lobed, lobes nearly equal in length, the middle lobe shortest obtuse rounded, lateral lobes large spreading puckered, with inner margins incurved and much rumpled and inflated, somewhat like two sub-calli, each with a large ochraceous spot or dash. Stamens inserted near base of corolla, stout, glabrous, flexuous, about half as long as corolla; anthers reniform-orbicular, mucronate; light umber-brown. Style thick and dilated at top, glabrous, with a few (5–6) scattered microscopic glandular hairs near top. Stigma large, recurved, bilobed; lobes globular, spreading, purple, finely papillose; finally exserted. Ovary ovoid. Hab. Parasitical on the roots of a small spreading Hydrocotyle (H. sibthorpioides, Col.), the foster plant originally brought from forests near Dannevirke, County of Waipawa; 1887: W. C. Obs. This plant is in many respects a remarkable and interesting one; especially if (as I at present believe) it should prove to be a new species, as such has not yet been detected in this country, nor in the Southern Hemisphere. I will therefore briefly give its history:— In 1887 I planted in a large-size flower-pot some Pterostylis, and Thelymitra tubers (these subsequently flowered), and with them a small neat Hydrocotyle, which I had also brought from the woods in the interior, as I wished to see its ripe fruit. The Hydrocotyle plant grew amazingly, throwing out scores of long filiform branches, 2ft.–3ft. long, and covered with flowers and fruit; and has proved to be—what I had supposed—a new species.* H. sibthorpioides, Col. (Vide description in Art. V., p. 83.) Suddenly (early in September,

1888) there appeared a large, closely-bracteated, purple head, rising from among the thickly-overgrown Hydrocotyle, and in a few days two more, strongly resembling the purple heads of asparagus in colour and form, only these were densely pilose. These heads grew very fast, and were soon found to be a species of Orobanche. They were all very much alike, merely differing in height, and, consequently, in the number of their flowers: one attained the height of 18in., with forty flowers; another 15in., with thirty-three flowers; and the third, 12in., with twenty flowers. And subsequently (about five to six weeks later) a fourth and similar one made its appearance. This plant differs considerably from all our British species (of which I have botanical drawings), and from the Australian “introduced” one described by Bentham (which is also European), and from several others whose descriptions I possess; still, there are more described, of which, however, I am ignorant, therefore this plant may yet come under one of these. I have no recollection of ever having seen the whole plant before; but, at the same time, I have a strong suspicion that I have noticed something arising from the thick beds of our largely-creeping pilose Hydrocotyle very much like what the heads of this plant were in their early incipient state.* See, for instance, a notice of an abnormal vegetable form observed (not wholly dissimilar) under H. concinna (“Trans. N.Z. Inst.,” vol. xvii., p. 239). This Orobanche in its earliest stage might easily have been confounded with such in the gloom of the forests. It is, however, new to science to find this parasite growing on Hydrocotyle; also, under cultivation; and then to have three (now four) together is equally rare. The foster plant, though exceedingly slender and delicate, is apparently as healthy and flourishing as ever.