C. ctenoides (comb-like); Fig. 20.—­Stem 3 in. to 5 in. high, and about 3 in. in diameter, egg-shaped, unbranched, rarely producing offsets at the base.  Ribs fifteen or sixteen, spiral, with closely-set cushions of stiff, whitish spines, which interlace and almost hide the stem; there are from fourteen to twenty-two spines to each cushion, and they are 1/4 in. long.  Flowers produced on the ridges near the top of the stem; tube short, spiny; petals spreading, like a Convolvulus, 3 in. to 4 in. across, bright yellow; stamens yellow, pistil white.  The flowers expand at about 9 a.m., and close again soon after noon.  They are developed in June or July.  This species is a native of Texas, and is rare in cultivation.  When not in flower it might easily be mistaken for Echinocactus pectinatus.  It should be grown in a sunny position, in a warm house or pit, all summer, and wintered on a shelf, near the glass, in a temperature of from 45 degs. to 50 degs. during winter.  Under cultivation it is apt to rot suddenly at the base, more especially when old.  Should this happen, the rotten parts must be cut away, and the wound exposed to the air in a dry house for a week or two.

[Illustration:  Fig. 20.—­Cereus ctenoides.]

C. enneacanthus (eight-spined); Fig. 21.—­Stem seldom more than 6 in. high by less than 2 in. in diameter, cylindrical in shape, bright green, simple when young, tufted in old specimens.  Ribs shallow, broad, irregular on the top, with spine-cushions on the projecting parts; spines straight, yellowish-white, semi-transparent, variable in length, longest about 1 in.  There are frequently as many as twelve spines in a tuft, although the specific name implies eight spines only.  Flowers on the ridges near the top of the stem, with spiny tubes, spreading petals of a deep purple colour, and yellow stamens and pistil.  They are developed freely in June and July.  This is a soft-fleshed species, from Texas; it is not easily kept in health, and is therefore rarely seen.  It should be treated as advised for C. ctenoides.  Neither of these plants will flower unless it is grown in a sunny position as near to the roof-glass as is possible.

[Illustration:  Fig. 21.—­Cereus enneacanthus.]

C. Fendleri (Fendler’s).—­One of the best of the dwarf-stemmed kinds.  It has a pale green stem, about 6 in. high, rarely branching at the base, but often found growing in clusters.  Ridges nine to twelve, running spirally round the stem, and bearing clusters of brown spines, some of them nearly 2 in. in length.  Flowers composed of a tube 1 in. long, green, fleshy, and spiny, with a spreading cup-like arrangement of petals and sepals, 3 in. in diameter, and of a bright purple colour; stigma and anthers green.  It produces its flowers in June.  It was introduced from the mountainous region of New Mexico about five years ago, and has blossomed freely in several collections, notably in that of Mr. Loder,