of layers of bristly wool and slender spines, amongst which the small
flowers are developed. The cap is persistent, and increases annually
with the stem.

2. MAMILLARIA. Stems short, usually globose, and covered with tubercles
or mammae, rarely ridged, the apex bearing spiny cushions; flowers
mostly in rings round the stem.

3. PELECYPHORA. Stem small, club-shaped; tubercles in spiral rows, and
flattened on the top, where are two rows of short scale-like spines.

4. LEUCHTENBERGIA. Stem naked at the base; tubercles on the upper part
large, fleshy, elongated, three-angled, bearing at the apex a tuft of
long, thin, gristle-like spines.

5. ECHINOCACTUS. Stem short, ridged, spiny; calyx tube of the flower
large, bell-shaped; ovary and fruit scaly.

6. DISCOCACTUS. Stem short; calyx tube thin, the throat filled by the
stamens; ovary and fruit smooth.

7. CEREUS. Stem often long and erect, sometimes scandent, branching,
ridged or angular; flowers from the sides of the stem; calyx tube
elongated and regular; stamens free.

8. PHYLLOCACTUS. Stem flattened, jointed, and notched; flowers from the
sides, large, having long, thin tubes and a regular arrangement of the
petals.

9. EPIPHYLLUM. Stem flattened, jointed; joints short; flowers from the