O. occidentalis (Western).—­Stem stout, woody, with innumerable branches, wide-spreading, often bent to the ground.  Joints 9 in. to 12 in. long by about 6 in. broad, flattened, as many as 100 on one plant.  Cushions nearly 2 in. apart, with small, closely-set bristles and straight spines from 1/2 in. to l1/2 in. long.  Flowers produced in June on the ripened joints, nearly 4 in. in diameter, orange-yellow.  Fruit 2 in. long, “very juicy, but of a sour and disagreeable taste.”  This is an exceptionally fine plant when allowed sufficient space to develop its enormous branches and joints; it is a native of the Western slopes of the Californian mountains.  It should be planted in a bed of rough, stony soil, in a dry greenhouse.  Possibly it is hardy, but it does not appear to have been grown out of doors in England.

O. Parmentieri (Parmentier’s).—­Stem erect.  Joints cylindrical, “like little cucumbers.”  Cushions about 1 in. apart, arranged in spiral rows, and composed of short, reddish bristles, with two or three straw-coloured spines, 1 in. long.  Flowers reddish, small.  The plant is a native of Paraguay, and is rarely heard of in cultivation.  It requires stove treatment.

O. Parryi (Parry’s).—­Stem short.  Joints club-shaped, 4 in. to 6 in. long, very spiny, the cushions elevated on ridge-like tubercles.  Bristles few, coarse, and long.  Spines very numerous, varying in length from 1/4 in. to 11/2 in.; central one in each cushion much the broadest, and flattened like a knife-blade, the others being more or less triangular.  Flowers yellowish-green, on the terminal joints, which are clothed with star-shaped clusters of bristle-like spines, the flowers springing from the apex of the joint, and measuring 11/2 in. across.  A native of Mexico, where it grows on gravelly plains.  This distinct plant is in cultivation at Kew, in a warm greenhouse, but it has not yet flowered.

O. Rafinesquii (Rafinesque’s); Fig. 84.—­A low, prostrate, spreading plant, seldom exceeding 1 ft. in height, the main branches keeping along the ground, the younger ones being erect.  The latter are composed of flat, obovate joints, 4 in. to 5 in. long by 3 in. in width, fresh green in colour; spines very few, mostly only on the upper edge of the last-made joints, single, or sometimes two or three from each spine-cushion, 1 in. long, straight, whitish, soon falling off; cushion composed of very fine reddish bristles and whitish wool; leaves very small, falling early.  The branches become cylindrical and woody with age.  Flowers 2 in. to 4 in. in diameter, bright sulphur-yellow, with a reddish tint in the centre; in form they are like a shallow cup, the numerous stamens occupying the middle.  They are produced in great abundance on the margins of the youngest joints, as many as fifty open flowers having been counted on a single specimen at one time.  Fruit pear-shaped, 11/2 in. to 2 in. long, naked, edible, somewhat acid and sweetish.  The flowering season is from July