xpand
only when the sun shines on them, closing up again in dull light, but
opening again, and remaining fresh for about a week. Introduced in 1850.
Flowers in March and April. This plant may be grown in a cool, sunny
greenhouse, or window, requiring only protection from frost in winter,
and in summer plenty of light, with a moderate amount of water. There
are several varieties of it described, their differences being chiefly
in the shape of the stem.

[Illustration: FIG. 47.--ECHINOCACTUS UNCINATUS.]

E. viridescens (greenish).--Stem 1 ft. high and 9 in. across, young
plants being broader than high; the sides split up into about twenty
ridges, which are again divided into knotty tubercles or waves. The
spines are remarkable for their size and strength, those on large plants
being 4 in. long by 1/2 in. broad at the base, gradually narrowing to a
stiff point; there are four central spines of this size, the others, of
which there are about a dozen, being shorter and thinner, and arranged
stellately. The flowers, which are rarely produced, are poor in
comparison with the majority of the flowers of this genus. As the name
denotes, their colour is yellowish-green; and they are about 11/2 in. wide
and high. There are often as many as a dozen flowers expanded together
on a stem of this plant when wild, and they are arranged in a circle
around the growing point. The interest in this species, however, centres
in its spines rather than its flowers. It is a native of the dry hills
of California, extending sometimes down to the sea-beach. There is a
plant of it at Kew 6 in. high and about fifteen years old; it has not
been known to flower there. Mr. Peacock also possesses a large plant of
it.

E. Visnaga. (visnaga means a toothpick among the Mexican settlers); Fig.
48.--Of the most remarkable features of this truly wonderful Cactus we
have already spoken earlier in this Chapter. In 1846, Sir W. J. Hooker
described, in the Illustrated London News, a large plant of it, which
had been successfully introduced alive to Kew, and which, a year or so
later, flowered, and was figured in the Botantical Magazine (4559). Its
height was 9 ft., and it measured 91/2 ft. in circumference; its weight a
ton. Afterwards, it exhibited symptoms of internal injury. The inside
became a putrid mass, and the crust, or shell, fell in by its own
weight. The shape of the stem is elliptical, with numerous ridges and
stout brown spines arranged in tufts alon