[Illustration:  Fig. 53.—­Echinopsis Pentlandi longispinus.]

E. tubiflorus (tube-flowered).—­This species has an orange-shaped stem, about 4 in. high, and divided into about twelve prominent, sharp-angled ridges, along which are tufts of blackish spines, 1/2 in. long, and set in little cushions of white wool.  The flower springs from the side of the stems, where it replaces a tuft of spines, and, as in E. Eyriesii, the tube is remarkably long, whilst the size of the whole flower much exceeds that of the rest of the plant, the length of the tube being about 6 in., and the width of the flower over 4 in.  The petals are pure white, recurved, displaying the crown of yellow stamens, arranged in a ring about the rather small, rayed stigma.  The tube is uniformly green, except that the scale-like bracts are edged with long, blackish, silky hairs.  A native of Mexico; introduced about fifty years ago, when it was figured in the Botanical Magazine and elsewhere as a species of Echinocactus.  E. tubiflorus may be placed along with E. Eyriesii and E. oxygonus, as it requires similar treatment.  The three kinds here mentioned may be recommended as a trio of very fine-flowered, small-stemmed Cacti, which may be grown successfully in any ordinary greenhouse.

CHAPTER IX.

THE GENUS MELOCACTUS.

(From melon, a melon, and Kaktos, a name applied by Theophrastus to a spiny plant; the species are melon-formed, and their angles are beset with tufts of spines.)

This genus forms a group of well-marked and curious plants, with stems similar to those of the globose Echinocactuses and floral characters quite distinct from all other genera.  They cannot be said to possess any particular beauty, as their stems are stiff and dumpy, their spines large and rigid, and their flowers small and unattractive.  But what is wanting in beauty of form or colour is atoned for in the cap which crowns the stem, and forms the flower-head, growing taller and taller whilst the stem remains stationary, till, under favourable circumstances, a cylindrical mass of spines and hairs, not unlike a large bottle-brush, and 1 ft. or more in length, is developed before the whole plant succumbs to old age.  This character belongs more particularly to M. communis, the commonest species, and the one best known in English gardens.  Additional interest attaches to this species, from the fact of its having been the first Cactus introduced into Europe, for we are informed that in the year 1581 living plants of the Melon Cactus were known in London.  Fifty years later, Gerard, the Adam of English gardening, wrote:  “Who can but marvel at the care and singular workmanship shown in this Thistle, the Melocarduus echinatus, or Hedgehog Thistle?  It groweth upon the cliffes and gravelly grounds neere unto the seaside in the islands of the West Indies, called St. Margaret’s and St. John’s Isle, neere unto Puerto Rico,