easuring nearly 2 in. across. This
species is a native of Mexico; it grows and flowers freely if kept in a
warm house.

[Illustration: FIG. 88. PERESKIA ZINNIAEFLORA.]

CHAPTER XVI.

THE GENUS RHIPSALIS.

(From rhips, a willow-branch; referring to the flexible, wand-like
branches of some of the kinds.)

About thirty species of Rhipsalis are known, most of them more peculiar
than ornamental, although everyone is in some way interesting. They are
remarkable for the great variety in form and habit presented by the
different kinds, some of them much less resembling Cactuses than other
plants. Thus, in R. Cassytha, the long, fleshy, whip-like branches and
white berries are very similar to Mistletoe; R. salicornoides, with its
leafless, knotty branches, resembles a Salicornia, or Marsh Samphire;
another is like a Mesembryanthemum; and so on. The flowers are usually
small, and composed of numerous linear sepals and petals, arranged more
or less like a star, with a cluster of thin stamens in the centre, and
an erect, rayed stigma. In the flat-jointed kinds, the flowers are
developed singly, in notches along the margins of the young, ripened
joints; in the knotted, Samphire-like kinds, they are borne on the ends
of the branches; and in those with short, fleshy, leaf-like joints, they
are usually placed on what appear to be flower-joints. Although the
branches of these plants are usually altogether unlike the rest of the
Order, yet occasionally they develop joints which are furrowed, and bear
clusters of spines exactly as in the commoner forms of Cactuses.

The geographical distribution of Rhipsalis is exceptional. It is the
only genus of Cactuses that has representatives in the Old World,
excluding, of course, those which have been introduced by man. The bulk
of the kinds of Rhipsalis occur in Central and South America, and the
West Indies; but one--viz., R. Cassytha--is also found in Africa,
Mauritius, Madagascar, and Ceylon, as well as in tropical America.
Several other species are found in Madagascar, some of them only recent
discoveries. The occurrence of similar or even identical plants in
tropical America and Madagascar has its analogy in the Animal Kingdom as
represented in the two countries.

Cultivation.--All the species appear to grow well and flower freely
under cultivation, the slowest grower being, perhaps, R. sarmentacea. In
their natural homes they are invariably found either on trees or rocks,
se