d near the outside of the top. Native of Mexico; in
meadows and thickets near Zimapan, at 5000 ft. elevation. It thrives with
us when grown in a frame in summer, and wintered in a cool greenhouse or
frame.

[Illustration: FIG. 70. MAMILLARIA SEMPERVIVA.]

M. senilis (hoary).--Stem about 3 in. high, spherical, unbranched,
except when very old, when it becomes proliferous at the base; tubercles
crowded, small, arranged spirally, and crowned with clusters of long,
radiating spines, which are almost white, hair-like, and become thickly
interwoven, as in the Old Man Cactus (Pilocereus senilis). The central
spine is black, and hooked at the tip. Flowers on the top of the stem,
near the centre; the petals toothed, spreading, and forming a deep cup,
with a cluster of tall stamens standing erect in the middle; colour
bright scarlet. The flowers, which appear in summer, remain open about
eight hours. Native country unknown; cultivated in France in 1845. This
plant is difficult to preserve in health, the best method being that of
grafting it on to a short Cereus, or a robust kind of Mamillaria, such
as M. cirrhifera. It is a pretty plant at all times, even when dead, for
we have seen plants of it preserve the appearance of live specimens long
after they have rotted and dried up in the centre, nothing remaining but
the shell formed by the skin and silvery spines. There is a close
resemblance between this species and M. Grahami.

M. stella-aurata (golden star).--This little plant obtains its name
from the rich golden-yellow of its stellate clusters of spines, which
are arranged thickly on the tips of the small, pointed tubercles. It
belongs to the group called Thimble Cactuses, of which it is one of the
prettiest. The stems are tufted, branching freely at the base, and
rising to a height of about 2 in. Flowers small, whitish, and much less
ornamental than the berry-like fruits which succeed them, and which are
egg-shaped, 1/2 in. long, and a deep rose-colour. M. tenuis is a variety of
this, with almost white spines. Native of Mexico. Introduced 1835. May
be cultivated under a bell-glass in a room window, the only danger being
damp during winter, which must be carefully avoided.

M. sub-polyhedra (usually many-sided); Fig. 71.--Stem simple till it
becomes old, when it develops offsets at the base, broadly cylindrical,
8 in. high, 5 in. in diameter. Tubercles four-sided at base, prism-shaped,
bearing pads of white wool in the corne