ures. Flowers funnel-shaped,
resembling Canterbury Bells, borne in a cluster on the summit of the
plant; ovary short and scaly; petals joined at the base, and coloured a
rosy-purple, dashed with yellow; the stamens fill the whole of the
flower-tube and are white; style a little longer than the flower-tube,
and bearing a ray of about a dozen stigmas. Fruit globose, as large as a
plum, and coloured cherry-red. The pulp is bright, crimson, and contains
a few brownish seeds. In the engraving the fruit is shown on the left,
and a flower-bud on the right. This species is often known in
Continental collections as P. Fosterii.

[Illustration: FIG. 56. PILOCEREUS HOULLETIANUS.]

P. senilis (Old-Man).--Stem attaining a height of 25 ft., with a diameter
of about 1 ft.; ridges from twenty-five to thirty on plants 4 ft. high;
the furrows mere slits, whilst the tufts of thin, straight spines, 1 in.
long, which crown each of the many tubercles into which the ridges are
divided, give young stems a brushy appearance. About the upper portion
of the stem, and especially upon the extreme top, are numerous white,
wiry hairs, 6 in. or more long, and gathered sometimes into locks. To
this character, the plant owes it name Old-Man Cactus; but, by a curious
inversion of what obtains in the human kind, old plants are less
conspicuous by their white hairs than the younger ones. Some years ago,
there were three fine stems of this Cactus among the cultivated plants
at Kew, the highest of which measured 181/2 ft. There was also, however, a
fine specimen in the Oxford Botanic Gardens, with a stem 16 ft. high; and
it is stated that this plant has been in cultivation in England a
hundred years at least. A plant twenty-five years old is very small,
and, from its slowness of growth, as well as from the reports of the
inhabitants of Mexico, where this species is found wild, there is reason
to believe that a stem 20 ft. high would be several hundred years old.
The flowers of P. senilis are not known in English collections, the
plant being grown only for its shaggy hairiness.

Other species are: P. chrysomallus, which has a branching habit, P.
Bruennonii (Fig. 57), P. Celsianus, P. columna, P. tilophorus, known only
in a young state, and several others, all very remarkable plants, but
not known in English collections, unless, perhaps at Kew.

[Illustration: FIG. 57. PILOCEREUS BRUeNNONII.]

CHAPTER XI.

THE GENUS MAMILLARIA.

(From mamilla, a