the colossal Cereus giganteus,
whose straight stems when old are as firm as iron, and rise with many
ascending arms or rear their tall leafless trunks like ships' masts to a
height of 60 ft. or 70 ft. From this we descend through a multitude of
various shapes and sizes to the tiny tufted Mamillarias, no larger than
a lady's thimble, or the creeping Rhipsalis, which lies along the hard
ground on which it grows, and looks like hairy caterpillars. In form,
the variety is very remarkable. We have the Mistletoe Cactus, with the
appearance of a bunch of Mistletoe, berries and all; the Thimble Cactus;
the Dumpling Cactus; the Melon Cactus; the Turk's cap Cactus; the
Rat's-tail Cactus; the Hedgehog Cactus; all having a resemblance to the
things whose names they bear. Then there is the Indian Fig, with
branches like battledores, joined by their ends; the Epiphyllum and
Phyllocactus, with flattened leaf-like stems; the columnar spiny Cereus,
with deeply channelled stems and the appearance of immense candelabra.
Totally devoid of leaves, and often skeleton-like in appearance, these
plants have a strange look about them, which is suggestive of some
fossilised forms of vegetation belonging to the past ages of the
mastodon, the elk, and the dodo, rather than to the living things of
to-day.

By far the greater part of the species of Cactuses belong to the group
with tall or elongated stems. "It is worthy of remark that as the stems
advance in age the angles fill up, or the articulations disappear, in
consequence of the slow growth of the woody axis and the gradual
development of the cellular substance; so that, at the end of a number
of years, all the branches of Cactuses, however angular or compressed
they originally may have been, become trunks that are either perfectly
cylindrical, or which have scarcely any visible angles."

A second large group is that of which the Melon and Hedgehog Cactuses
are good representatives, which have sphere-shaped stems, covered with
stout spines. We have hitherto spoken of the Cactuses as being without
leaves, but this is only true of them when in an old or fully-developed
state. On many of the stems we find upon their surface, or angles, small
tubercles, which, when young, bear tiny scale-like leaves. These,
however, soon wither and fall off, so that, to all appearance, leaves
are never present on these plants. There is one exception, however, in
the Barbadoes Gooseberry (Pereskia), which bears tr