E. mamillosus (nipple-bearing).—­A short, dumpy plant, with numerous tubercled ridges, bearing bunches of dark brown hair-like spines, which form a close network about the stem.  The flowers are developed on the top of the stem, and are about 4 in. in diameter, with a thick tube; the petals are spreading, bright yellow in colour, and arranged in a regular, bell-like whorl.  Inside this bell is a circle of purple filaments or stamens, forming a pretty contrast with the clear yellow of the petals.  This is a recent introduction, which flowered in the Kew collection for the first time in June, 1886.  It is one of the most beautiful of the large-flowered kinds, and, as it thrives in a warm greenhouse and is very free-flowering, it may be expected to become a favourite with Cactus growers.  Owing to the lack of information respecting the conditions under which many of the Cactuses are found wild, and to the fact that little in the way of experimental culture has been done by growers of this family, cultivators are sometimes in the dark as regards the lowest temperature in which the rarer kinds can be safely grown.  Many of the species of the present genus, for instance, were grown in stoves years ago but are now known to thrive in a cool greenhouse where frost alone is excluded.

E. multiflorus (many-flowered); Bot.  Mag. 4181.—­A well-named Cactus, as its small stem (seldom more than 5 in. high, and the same in width) often bears a large cap-like cluster of beautiful white flowers, except for a slight tinge of brown on the tips of the petals.  Each flower is composed of a green, scaly tube, and several rows of reflexed petals, which form a shallow cup 21/2 in. across.  The stamens are tipped with orange-coloured anthers, and the stigma is rayed and snow-white.  The stem is ridged with rows of fleshy mammae or tubercles, which are curiously humped, and each bears a cluster of spreading, brown spines, 1 in. long.  The number of flowers this little plant annually produces seems more than could be possible without proving fatal to its health; but we have seen it blossom year after year, and in no way has its health appeared impaired.  It may be grown on a shelf in a warm greenhouse, or in the window of a heated dwelling-room.  Introduced, probably from Mexico, in 1845.  This, like all the small, globular-stemmed kinds, may be grafted on the stem of a Cereus of suitable thickness.  Some cultivators believe that grafting causes the plants to flower more freely, but we have not observed any difference in this respect between grafted and ungrafted plants.

E. myriostigma. (many-dotted); Fig. 40.—­In the form of the stem of this species we have a good illustration of how widely a plant may differ from others of the same genus in certain of its characters, for the spines are almost totally suppressed, and the ridges are regular, deep, and smooth.  There are usually five or six ridges, a transverse section of the stem revealing a form exactly like the common