[Illustration:  Fig. 74.  Leuchtenbergia principis.]

Species.

L. principis (noble); Fig. 74.—­This, the only species known, was introduced from Mexico to Kew in 1847, and flowered the following year.  The plant attains a height of 1 ft. or more, the stem being erect, stout, clothed with the persistent, scale-like bases of the old, fallen-away tubercles, the bases having dried up and tightened round the stem.  The upper part is clothed with the curved, leaf-like tubercles, from 3 in. to 6 in. long, grey-green in colour, succulent, with a tough skin, triangular, and gradually narrowed to a blunt point, upon which are half a dozen or more thin, flexuous, horny filaments, neither spines nor hairs in appearance, but almost hay-like; the central one is about 5 in. long, and the others about half that length.  The flowers are borne on the ends of the young, partly-developed tubercles, near the centre of the head; they are erect, tubular, 3 in. to 4 in. long, scaly, gradually widening upwards; the sepals and petals are numerous, and form a beautiful flower of the ordinary Cactus type, quite 4 in. across, and of a rich, clear yellow colour.  The anthers, which also are yellow, form a column in the centre, through which the nine-rayed stigma protrudes.  Strong plants sometimes produce two flowers together.

CHAPTER XIII.

THE GENUS PELECYPHORA.

(From pelekyphoros, hatchet-bearing; referring to the shape of the tubercles.)

Ike Leuchtenbergia, this genus is monotypic, and it is also rare, difficult to cultivate, and exceptionally interesting in structure.  It is closely related to the Mamillarias, as may be seen, by comparing the Figure here given with some of them; indeed, it was once known as M. asellifera, having been described under that name when first introduced, in 1843.  From Mamillaria, however, it differs in the form of its tubercles, which are hatchet-shaped, and cleft at the apex, where each division is clothed with small, horny, overlapping scales, not unlike the back of a woodlouse—­hence the specific name.

Cultivation.—­The Hatchet Cactus grows very slowly, specimens such as that represented in our Illustration being many years old.  We have seen healthy plants, freshly imported, grow for a few months, and then suddenly die, the inside of the stem rotting whilst outside it looked perfectly healthy.  It is always grown on its own roots, but probably it would thrive better if grafted on the stem of some dwarf Cereus or Echinocactus.

[Illustration:  Fig. 75.  Pelecyphora aselliformis.]

Propagation.—­The propagation of Pelecyphora is easiest effected by means of seeds, which, however, are not always procurable.  It is stated by Labouret, a French writer on Cactuses, that the first plants introduced arrived dead, but a few seeds were found in a withered fruit on one of the dead stems, and from these the first plants grown in Europe were raised.  M. de Smet of Ghent, had a large stock of this Cactus a few years ago, and a German nurseryman, H. Hildmann, of Oranienberg, near Berlin, usually has many young plants of it for sale.