E. Williamsii (Williams’s); Bot.  Mag. 4296.—­A very distinct dwarf species, often called the “Dumpling Cactus,” from the puffed-out, tumid appearance of its stems, which frequently branch at the base, so as to form a tuft of several heads; these are turbinate, 3 in. or 4 in. high, and 2 in. across the top, where the smooth, pale green flesh is divided into about half-a-dozen rounded tubercles, pressed closely together, and suggesting a number of small green potatoes joined by their bases.  Each tubercle bears several tufts of short hairs.  The flowers proceed from the young tubercles near the centre of the crown, their bases being enveloped in pale brown wool, the petals spreading out daisy-like to the width of 1 in., with a short disk of stamens in the middle; they are white, tinged with rose, and are developed in the summer months.  Native of the rocky hills of Mexico, whence it was introduced in 1845.  The stems of this plant are its most distinctive feature.  It thrives on a shelf in a warm greenhouse, if kept perfectly dry in winter, and it should be potted in a compost consisting of broken brick two-thirds, loam one-third.

E. Wislizeni (Wislizen’s); Fig. 49.—­A large-stemmed kind, second only in size to E. Visnaga.  Young plants have depressed stems, those in older specimens being cylinder-shaped.  A specimen at Kew is 8 in. high by 18 in. in diameter, with twenty-one ridges, which are regular and sharp-edged, and bear bunches of spines at regular intervals, the outer and shorter ones being spreading and white, whilst from the middle of each tuft arise four longer and stouter spines, three of them 2 in. long, and one 3 in., with the point hooked, and as strong as if made of steel.  The flowers, which are developed only on large plants, are greenish-yellow, about 2 in. long and wide, and expand during summer and autumn.  The juice of the stems is said to serve as a substitute for water when the latter is scarce, and instances have been known among the white trappers where the lives of men have been saved by this plant.  A novel use the stems are put to by the Indians is that of boilers, a purpose which they are said to answer well.  The fleshy inside is scooped out, and the tough skin, with its iron-like spine protection, is then filled with vegetables and water and placed on the fire.  As there is a plentiful supply of plants, the Indians do not trouble to carry this “boiler” about with them, but make a fresh one at every stage of their journeyings.

[Illustration:  Fig. 49.—­Spines and flowers of Echinocactus wislizenii.]

CHAPTER VIII.

THE GENUS ECHINOPSIS.

(From echinos, a hedgehog, and opsis, like.)