its flowers, the
attractive form of its stem, and its reputed hardiness. It will thrive
in a cold frame, and requires protection from excessive wet only, rather
than from cold. Grown in a warm house, it becomes sickly, and is
short-lived.

M. bicolor (two-coloured).--One of the commonest of the Cactuses grown
in English gardens, and one of the most distinct, owing to its short,
silvery hair-like spines, thickly crowded on the ends of the small
tubercles, completely hiding the stem from view. The latter is from 6 in.
to 1 ft. high, 3 in. in diameter, cylindrical, often branching into
several thick arms, when it has a quaint appearance. If kept free from
dust, which may be done by covering the plant with a bell glass, there
is much beauty in the stem; indeed, it is owing to this, rather than as
a flowering Cactus, that this species finds favour as a garden plant.
The flowers are less than 1 in. in length and width, stellate, their
colour deep purple; they are developed in June. Although a native of
elevated regions in Mexico (4000-5000 ft.), this plant thrives best when
grown in a warm house. There are several handsome and very old specimens
of it in the tropical collection of succulents at Kew. It is one of the
easiest to manage, and will thrive in a warm room-window if exposed to
bright sunlight and kept dry in winter. M. nivea and M. nobilis are both
varieties of this species.

M. chlorantha (greenish-yellow).--A newly-introduced species with
erect, cylinder-shaped stems, 6 in. high, clothed with numerous
tubercles, which are tipped with clusters of long, silvery, interlacing,
hair-like spines, and a few stouter blackish ones. The flowers are
described as greenish-yellow, so that they are not likely to add much to
the beauty of the plant, which is recommended because of the
attractiveness of its stem and spines. It is a native of Mexico and
Texas, whence it was introduced some two years ago. It requires
cool-house treatment, and should be kept free from dust, which
disfigures the white spines.

M. cirrhifera (twisted).--Like M. bicolor, this species owes its
frequent occurrence in gardens to the symmetry and neatly-chiselled form
of its stems, and not to any attraction possessed by its flowers. It
will thrive anywhere where the sun can shine upon it, if sheltered from
severe cold and wet. In a cottage window it may be grown, and kept for
many years, without losing health or, on the other hand, increasing much
in si