hence
the specific name. The stoutest spines are 3 in. long, and are sharp and
strong as needles. This species (which is probably a native of Mexico)
is deserving of a place in collections of Cactuses because of the
character of its spines. Probably it is only a variety of O. Tuna. It
requires warm-house treatment.

O. hystricina (porcupine-like).--This beautiful species was discovered
in the San Francisco Mountains mixed with O. missouriensis, to which it
is nearly allied. It is spreading in habit, the joints 3 in. to 4 in. long
and broad; cushions 1/2 in. apart, rather large, with numerous spines,
varying in length from 1/2 in. to 4 in., and short, yellowish bristles.
Flowers large, yellow. Fruit 1 in., long, spiny. This plant is not known
in English collections, but it is described by American botanists as
being attractive and a free grower. As it is found along with O.
missouriensis, it ought to prove hardy in England.

O. leptocaulis (slender-stemmed).--This little Mexican species is
chiefly remarkable for its fragile, numerous, twig-like joints, thickly
dotted with tubercles and numerous spirally-arranged cushions of reddish
bristles, with long, grey spines. It does not flower under cultivation.
Requires stove treatment.

O. leucotricha (white-haired).--An erect-stemmed kind, with flattened
joints, ovate or oblong in shape, and bearing numerous cushions, 1/2 in.
apart, of short bristles, with a large, central spine, and a few others
rather shorter. When young these spines are rigid and needle-like; but
as they get older they increase in length, and become soft, and curled
like stiff, white hair. Young plants are noticeable for their small,
subulate leaves of a bright red colour, whilst old examples are almost
as interesting as the Old Man Cactus (Pilocereus senilis), the long,
white, hair-like spines of the Opuntia hanging from the older joints in
much the same manner as they do from the upper part of the stem of the
Pilocereus. Flowers yellow, produced in June. This species is a native
of Mexico, and requires stove treatment. Seeds of this, and, indeed, of
a large proportion of the cultivated Opuntias, may be procured from
seedsmen, and as they germinate quickly, and soon produce handsome
little plants, a collection of Opuntias is thus very easily obtained.

O. macrocentra (large-spurred).--A flat-jointed species, growing to a
height of 3 ft.; the joints large, almost circular, thinly compressed,
and usually