species we have a good illustration of how widely a plant may
differ from others of the same genus in certain of its characters, for
the spines are almost totally suppressed, and the ridges are regular,
deep, and smooth. There are usually five or six ridges, a transverse
section of the stem revealing a form exactly like the common star-fish
(Astrophyton), a resemblance to which the name Astrophytum, sometimes
applied to this plant, owed its origin. The form of the stem is well
represented in the Figure. The white dots shown on the bark, and which
look like scales, are composed of very fine interwoven hairs, which,
under a microscope, are very pretty objects. This species was introduced
from Mexico along with the large plant of E. Visnaga described at the
beginning of this chapter, and was first flowered at Kew, in July, 1845.
Stems 1 ft. in length were received, along with shorter ones; but only
the small ones were established. The flowers are daisy-like, 11/2 in.
across, and are straw-coloured, the petals being tipped with black. It
thrives under warm greenhouse treatment. When without its flowers, it
looks more like a piece of chiselled stone than a living plant.

[Illustration: FIG. 40.--ECHINOCACTUS MYRIOSTIGMA.]

E. obvallatus (fortified); Fig. 41.--The form of stem in this species
is shown in the Figure. It grows very slowly plants 4 in. through taking
about ten years to reach that size from seeds. The spines are stout, all
deflexed, and arranged along the edges of the numerous ribs into which
the stem is divided. The flowers are developed from the centre of the
plant, and are surrounded by the erect spines, which crown the, as yet,
undeveloped tubercles. Two or three flowers are produced at about the
same time, each one being composed of a short, spiny tube, and a whorl
of erect petals, which are pointed, purple-coloured, paler at the
margin, the stamens being yellow. Native of Mexico. It requires a stove
temperature, and flowers in summer.

[Illustration: FIG. 41.--ECHINOCACTUS OBVALLATUS.]

E. Ottonis (Otto's); Bot. Mag. 3107.--A dwarf kind, with a
balloon-shaped stem, rarely exceeding 4 in. in height, and divided into a
dozen wide ridges with sharp, regular edges, along which are clusters of
small, brown spines, set in little tufts of wool, and looking like an
array of spiders. The flowers are borne on the tops of the ridges, and
are pale yellow in colour, with a band of red hair-like spines
surrounding th