[Illustration:  Fig. 47.—­Echinocactus uncinatus.]

E. viridescens (greenish).—­Stem 1 ft. high and 9 in. across, young plants being broader than high; the sides split up into about twenty ridges, which are again divided into knotty tubercles or waves.  The spines are remarkable for their size and strength, those on large plants being 4 in. long by 1/2 in. broad at the base, gradually narrowing to a stiff point; there are four central spines of this size, the others, of which there are about a dozen, being shorter and thinner, and arranged stellately.  The flowers, which are rarely produced, are poor in comparison with the majority of the flowers of this genus.  As the name denotes, their colour is yellowish-green; and they are about 11/2 in. wide and high.  There are often as many as a dozen flowers expanded together on a stem of this plant when wild, and they are arranged in a circle around the growing point.  The interest in this species, however, centres in its spines rather than its flowers.  It is a native of the dry hills of California, extending sometimes down to the sea-beach.  There is a plant of it at Kew 6 in. high and about fifteen years old; it has not been known to flower there.  Mr. Peacock also possesses a large plant of it.

E. Visnaga. (visnaga means a toothpick among the Mexican settlers); Fig. 48.—­Of the most remarkable features of this truly wonderful Cactus we have already spoken earlier in this Chapter.  In 1846, Sir W. J. Hooker described, in the Illustrated London News, a large plant of it, which had been successfully introduced alive to Kew, and which, a year or so later, flowered, and was figured in the Botantical Magazine (4559).  Its height was 9 ft., and it measured 91/2 ft. in circumference; its weight a ton.  Afterwards, it exhibited symptoms of internal injury.  The inside became a putrid mass, and the crust, or shell, fell in by its own weight.  The shape of the stem is elliptical, with numerous ridges and stout brown spines arranged in tufts along their edges.  The flowers are freely produced from the woolly apex; the tube is scaly and brown, and the petals are arranged like a saucer about the cluster of orange-coloured stamens.  The colour of the petals is bright yellow, and the width of the flower is nearly 3 in.  This plant is a native of Mexico, and is usually cultivated in a tropical temperature, but it would probably thrive in a warm greenhouse.  It flowers in summer.  As we have stated, large specimens do not live long in this country; and as the flowers are only borne by such, the plant, except only for its stems, is not to be recommended for ordinary collections.

[Illustration:  Fig. 48.—­Echinocactus visnaga.]