O. Davisii (Davis’); Bot.  Mag. 6652.—­Stems somewhat horizontal, not exceeding 11/2 ft. in height; joints 4 in. to 6 in. in length, and about 1/2 in. in thickness; wood dense, and hard when old; tubercles not prominent, bearing cushions of very slender bristles, forming a kind of brush, from amongst which the spines spring.  The longest spines are 11/2 in., and they are covered with a loose, glistening sheath.  Flowers 2 in. in diameter, greenish-brown.  The plant is a native of New Mexico, and was introduced in 1883.  It forms a compact, shrubby little plant if grown in an intermediate house during winter, and placed in the open in full sunshine during summer.  It was flowered for the first time in England in 1883, and although not what we should call an attractive plant, in America it is described as being “a well-marked and pretty species.”  It is named after Jefferson Davis, the American statesman.

O. decumana (great-oblong).  This is the largest-growing species in cultivation.  At Kew it is represented by a plant 12 ft. high (it would grow still taller if the house were higher).  It has a hard, woody, brown-barked stem, bearing an enormous head of very large, elliptical, flat joints, 12 in. to 20 in. long, and about 1 ft. broad, smooth, grey-green, with a few scattered cushions of very tiny bristles, and sometimes, though rarely, a spine or two.  Flowers large, orange-coloured, produced in summer.  Fruit oval, 4 in. long, spiny, brownish-red, very watery when ripe; flesh red, sweet.  A native of Brazil, and requiring stove treatment.  This is said to be what is known in Malta as the Indian Fig.  The plant is chiefly interesting here on account of the extraordinary size of the joints.

O. diademata (diademed).—­A small, remarkable, and extremely rare little species, with a short, erect stem, composed of globose, superposed joints, grey-green in colour, and very succulent.  The topmost joint is pear-shaped, with a tuft of whitish hair and spines on the apex, out of which the new growth pushes.  Cushions large, about 1 in. apart, furnished with a tuft of short, grey hairs and short spines, with a large one at the base.  The character of this large spine is exceptional, being broad, flat, cartilaginous, whitish, and curving downwards.  On healthy large examples these spines are 2 in. long, and nearly 1/4 in. wide at the base.  Flowers and fruit not known.  Native of Mendoza (La Plata).  This little plant requires to be cultivated in a warm greenhouse or stove, but it grows very slowly.  It is certainly a most interesting Cactus; examples of it may be seen at Kew, where there is a plant which, although over ten years old, is only 4 in. high.  Syns.  O. platyacantha and Cereus syringacanthus.