E. centeterius (many-spined); Bot.  Mag. 3974.—­This has a conical-shaped stem, 6 in. high by 4 in. wide, with about fourteen ridges, which are notched, and bear star-shaped clusters of pale brown spines, 1/2 in. long.  The blossoms are borne rather thickly on the summit of the stem, from six to nine flowers being sometimes open together; and as they are each nearly 3 in. across, and of good substance, they present an attractive appearance.  The petals are of a deep straw-colour, with a reddish streak down the centre, and 11/2 in. long, with the apex notched or toothed.  The stamens are spirally coiled round the stigma, which is club-shaped and white.  This species is probably a native of Mexico, and was first flowered in England at Kew, in 1841.  A cool, dry greenhouse suits it best; or it may be grown in a sunny room window where frost would not be allowed to reach it in winter.  Unless subjected to very dry treatment during the winter months, and also kept in a position where all the sunlight possible would reach it—­even when at rest—­there is not much chance of this plant producing its large flowers.  It may be kept alive by giving it uniform treatment all the year round, but it would never flower.

E. cinnabarinus (cinnabar-flowered); Bot.  Mag. 4326.—­This is another of the Mamillaria-like kinds, and is remarkable for the depressed form of its stem, which may be likened to a sea urchin, both in size and shape.  Old plants are from 6 in. to 8 in. in diameter, and about 4 in. high; the spiral formed by the tubercles rises very gradually, and each of the latter is surmounted by a tuft of strong, brown, radiating spines, imbedded in a little cushion of wool.  The flowers spring from the outside of the depressed top of the stem, two or three opening together and forming a beautiful picture, both as to size and colour.  The tube is short and green, with a row of long green sepals at the top, and above these the petals, which are 2 in. long, overlapping, recurved, the edges toothed, and the colour a brilliant cinnabar-red.  The stamens are in two series, very numerous, and the anthers are bright yellow.  Looking at the flattened, spiny stem, it seems impossible that such large, handsome flowers should be produced by it.  A native of Bolivia; introduced about 1846.  It blossoms in July, and may be grown on a shelf in a cool greenhouse, as advised for the E. centeterius.

E. concinnus (neat); Fig. 29.—­A small species with a globose stem, 2 in. high and 3 in. wide, and about twenty ridges, which are rounded, rather broad, each bearing about half-a-dozen little bunches of spines arranged in a star.  The flowers are numerous, as large as, or larger than, the stem, being 3 in. long and broad, the tube covered with brown hair-like spines, and having a few reddish scales, whilst the petals are in several rows, overlapping, with pointed tips, and are coloured dark yellow with a red streak down the centre.  Several flowers are sometimes