TRIBUS: VANDEAE - Lindley.
ONCIDIUM. - Swartz. Act. Holm. 239. 1800. Brown in Hort. Kew. 5. 215.
AN EPIPHYTE. PSEUDOBULBS deeply sulcated, ovate, tapering towards the apex, compressed at the edges, from 2 to 4 inches long, throwing out numerous slender wiry roots. LEAVES sword-shaped, a foot or more long, one and sometimes two on each pseudo-bulb. SCAPE, 3-4 feet high, quite erect, bearing from its very commencement numerous branches, on which the flowers are rather loosely scattered. SEPALS and PETALS nearly equal, oblong, obtuse, spread wide open, of a bright green color, blotched with a rich reddish brown. LIP pure white, lobed; the lateral lobes small, rounded; the middle lobe broadly kidney-shaped, emarginate. CREST, consisting of 5 tubercles, of which the two outer are thin and sharp, the 2 inner fleshy and straight, and the middle one, (which is much the largest,) resembling in form the horn of a rhinoceros, pointing towards the base. WlNGS of the COLUMN crenulate, scimitar-shaped, of a faint rose-color.The extensive genus Oncidium, which now comprehends upwards of sixty species, contains none more distinct or remarkable, we had almost said, more beautiful, than our present subject. In habit Oncidium leucochilum is large and stately, and approaches Oncidium altissimum, Baueri, and Oncidium pictum; but its flower-stems have the peculiarity of being branched from the very base, which we have never observed in any other species. Its most characteristic feature is, however, the well-proportioned pure white labellum, which contrasts agreeably with the dark-green sepals and petals. The rose-colored wings of the column likewise add to the elegance of the flower. In Oncidium pulchellum (which offers the only other known example of a white labellum), not only is the habit totally different, but the lip is spotted. Something like a white labellum is found in a little species, called Oncidium lunatum; but it is a very dirty white, and also blotched with brown. towards the center with yellow, and is so large as nearly to conceal the sepals and petals, which, like itself, are white.
The roots of Oncidium leucochilum are produced in great abundance, and are of a very fine wiry texture. As an example of a directly opposite character, we may instance Oncidium Cavendishianum (Tab. III., of this Work) of which the roots are few, but the thickest in the genus. The pseudobulbs of Oncidium leucochilum press closely upon one another, so that the roots get cramped and entangled amongst them in hopeless confusion, and to such an extent as almost to bury the poor tubers alive. When, on the arrival of a collection of Orchidaceae from abroad, a case of this description is observed, strong measures must be immediately resorted to; for although the love of fine specimens may plead against the dismemberment of so large a mass of bulbs so "full of lusty life," still it is next to impossible to cultivate the species with any success till it has been freed from this incubus of rubbish and roots. The latter have usually lost their vitality on their arrival; and if not, they soon become rotten when subjected to a moist heat; they are, therefore, apt to occasion the decay of the pseudo-bulbs, and at the same time are incapable of contributing in any way to their support. They are therefore to be removed carefully and speedily, which is not to be effected without breaking up the masses into pieces, each containing 3 or 4 pseudobulbs; and if among these any decayed ones be observed, they must at once be cut away. Besides the danger to be apprehended from decomposition, these collections of roots afford a secure retreat to a species of "Cockroach," of which we shall hereafter speak, and than which, Orchidaceae have no greater foe.
Oncidium leucochilum appears to be not uncommon in Guatemala, where it was found by Mr. Skinner, and sent to us in 1835; and in the autumn of the following year was produced the specimen from which our figure is taken.