Dischidia
(from dischides, twice-cleft; referring to the bifid segments of the corona). ORD. Asclepiadeae. A genus of stove evergreen perennial trailers. There are about twenty-four species, natives of the East Indies, Malayan Archipelago, and tropical Australia. Flowers white or red, small, sub-umbellate. Leaves opposite, roundish, thick, fleshy. Stems rooting at the joints. For culture, see Hoya.
D. benghalensis (Bengalese). fl., corollas small, urceolate; umbels few-flowered, from alternate axils, on short peduncles. September. l. oblong-lanceolate, two-edged, flat. India, 1818. (B. M. 2916.)
D. nummularia (Moneywort-leaved). fl. very small, in little sessile, axillary or interpetiolar clusters; calyx segments minute, corolla under one-and-a-half 1ines long; tube inflated; lobes narrow, longer than the tube; corona segments subulate. August. l. on very short petioles, nearly orbicular, thick, fleshy, not exceeding 1/2in. in diameter. h. 6in. Queensland. A succulent milky-juiced epiphyte, more or less mealy-white.
DISEASES. Many plants are subject to no Disease, although they may be particularly so to insect pests. Others, again, are susceptible to Disease at any stage of growth, and when it is often very difficult to know the cause from which the evil proceeds. Canker, Gumming, and Mildew are destructive Diseases to fruit-trees and plants. The cause of the first cannot be traced in many cases; while in others it may be discovered too late for applying a remedy, even if this were practicable. Gumming and Mildew are caused by Fungi. The progress of Disease in plants may often be stopped if measures are taken, when it is first detected, to find and, if possible, remove the cause. When once established, it is far more difficult to cure, or even check; fatal results being often the ultimate consequence. Diseases being caused by forces acting apparently under such opposite conditions in similar or different plants, it is impossible to give instructions for their prevention generally. A cold and undrained soil, or that which is excessively rich, sudden changes of temperature, improper pruning, draughts, or, on the other hand, a too close or moist atmosphere, with many other like conditions, tend to promote Disease, and should be always guarded against Diseases arising from the growth of a fungus on any parts of plants, are often greatly encouraged by a warm, moist atmosphere. Some of this description are amongst the most destructive, and, as a rule, it is very difficult or impossible to effect a cure, when they become established. The fungi which are more or less superficial in their growth--that is to say, live on the surface of the tissues--may be checked by dusting with sulphur, &c.; those, like the Potato Disease (Peronospora), for instance, which send their threads into the body of the host plant, cannot be destroyed by any such means.