of the species, he may succeed in making out what the plant is.

For the classification of Cactuses, botanists rely mainly on their
floral organs and fruit. We may, therefore, take a plant of
Phyllocactus, with which most of us are familiar, and, by observing the
structure of its flowers, obtain some idea of the botanical characters
of the whole order.

Phyllocactus has thin woody stems and branches composed of numerous long
leaf-like joints, growing out of one another, and resembling thick
leaves joined by their ends. Along the sides of these joints there are
numerous notches, springing from which are the large handsome flowers.
On looking carefully, we perceive that the long stalk-like expansion is
not a stalk, because it is above the seed vessel, which is, of course, a
portion of the flower itself. It is a hollow tube, and contains the long
style or connection between the seed vessel and the stigma, a (Fig. 2).
This tube, then, must be the calyx, and the small scattered scale-like
bodies, b (Fig. 2), which clothe the outside, are really calyx lobes.

[Illustration: FIG. 2.--FLOWER OF PHYLLOCACTUS, CUT LENGTHWISE.

a, Calyx Tube. b, Calyx Lobes. c, Ditto, assuming the form of Petals. d,
Stamens. e, Style. f, Ovary or Seed Vessel.]

Nearer the top of the flower, these calyx lobes are better developed,
until, surrounding the corolla, we find them assuming the form and
appearance of petals, c (Fig. 2). The corolla is composed of a large
number of long strap-shaped pointed petals, very thin and delicate,
often beautifully coloured, and generally spreading outwards. Springing
from the bases of these petals, we find the stamens, d (Fig. 2), a great