purplish in colour. Cushions about 1 in. apart, with spines
often 3 in. long, of a greyish colour, and generally pointing downwards.
Flowers 3 in. across, bright yellow; they are developed in May and June,
on the upper edges of the youngest joints. This plant is a native of
Mexico; it is at present rare, but the unusual colour of the joints, its
compact, freely-branched habit, the extraordinary length of its spines,
and the size of its flowers, ought to win for it many admirers. It is
easily grown if kept in an intermediate house. Plants of it may be seen
in the Kew collection.

O. macrorhiza (large-rooted); Figs. 82, 83.--In this Texan species we
have a combination of the principal characters for which the genus
Opuntia is remarkable: The thick, fleshy roots, which are a supposed
source of food, and which look like potatoes; the cylinder-shaped older
stems, and the flattened, battledore-like joints; the tufts of bristles
on the stems, and deciduous, longer spines on the joints; the large,
beautiful, yellow flowers; and the small leaves on the newly-formed
joints. In habit and flowers this kind resembles O. Rafinesquii; and if
not quite hardy in England, it is nevertheless sufficiently so to thrive
in any sunny position where it would be protected from frost and
excessive wet. The accompanying illustrations represent the characters
of this species so well that further description is not needed. The
flowers are developed in early summer.

[Illustration: FIG. 82. FLOWERING BRANCHES OF OPUNTIA MACRORHIZA.]

[Illustration: FIG. 83. ROOTS OF OPUNTIA MACRORHIZA.]

O. microdasys (small, thick).--This is a handsome little Mexican plant.
Its flattened joints, which are nearly circular in outline, are thickly
covered with little cushions of bright orange-yellow bristles, the
cushions being so close together that the short bristles almost hide the
green joints from view. The stems are semi-decumbent, and they branch
somewhat freely. Flowers not seen. It thrives in a warm greenhouse
temperature. The best examples of this pretty Opuntia are grafted on a
robust-growing kind, the stock being about 1 ft. long, and the scion
forming a compact head of pretty, healthy-looking joints. Treated in
this way, this species is most interesting and attractive. It may also
be grown on its own roots. There is a variety of it, named rufida, in
which the bristles are reddish-brown.

O. missouriensis (Missouri).--A stout, prostrate kind, forming l