y in the apex of the
stems in the early part of the summer. The tube is very short, naked,
and completely hidden by the young mammae; sepals and petals in four
series, the outer one pale purple, the inner of a deep purple colour;
stamens very numerous, and the stigma has only four erect lobes. The
plant was first described from examples cultivated in Berlin in 1843,
but the flowers were not known till 1858. There are several varieties
known, viz., P. a. concolor, which is distinguished by the whole of the
flower being deep purple in colour; P. a. pectinata has larger scales
(spine-tufts); and P. a. cristata is, as its name denotes a kind of
cockscomb or crested form. They are all natives of Mexico.

CHAPTER XIV.

THE GENUS OPUNTIA.

(The old Latin name used by Pliny, and said to have been derived from
the city of Opus.)

There are about 150 species of Opuntia known, all of them natives of the
American continent and the West Indies, though a considerable number
have become naturalised in many other parts of the world. They are, with
very few exceptions, easily distinguished from all other Cactuses by the
peculiar character of their stems and spines; they are also well marked
in the structure of their flowers. They vary in size from small,
trailing, many-branched plants, never exceeding 6 in. in height, to large
shrubs 8 ft. to 30 ft. high. (Humboldt states that he saw "Opuntias and
other Cactuses 30 ft. to 40 ft. high.") Generally the branches are nearly
flat when young, and shaped like a racquet or battledore; but in some
species the branches are round (i.e., in O. cylindrica, O. subulata, O.
arborescens, &c.). All the kinds have fleshy stems, which ultimately
become cylindrical and woody. At first they consist of fleshy joints,
superposed upon one another, the joints varying considerably in size and
shape. When young they bear small fleshy leaves along with the
spine-tufts; but the former fall off at an early stage, whilst the
spines are altered in length or number as the joints get old. In one or
two kinds the spines fall away when the joints begin to harden, and in
O. subulata the leaves are large and persistent.

The nature of the spines of Opuntias is of a kind that is not likely to
be forgotten by anyone coming into contact with them. Every spine, from
the tiny bristles, hardly perceptible to the naked eye, to the stout,
needle-like spears which are found on the branches of some kinds, is
barbed, and