M. Schelhasii (Schelhas’).—­A pretty little tufted kind, its habit and size being shown in Fig. 69.  The stem produces offsets freely at the base, which grow into full-sized stems, and develop young ones, till a compact cushion is formed.  Tubercles closely arranged, cylindrical, shining green, with fifteen to twenty radial, white, hair-like spines, 1/2 in. long, and three inner ones, which are thicker, purplish in colour, usually only one being hooked.  Flowers white, with a line of rose down the middle of each petal, 3/4 in. across.  Flowering season, beginning of summer.  Native of Mexico.  It may be grown out of doors in a sunny position in summer, and wintered on a shelf in a greenhouse.

[Illustration:  Fig. 69.  Mamillaria Schelhasii.]

M. Schiedeana (Schiede’s).—­Stem globose, 3 in. to 5 in. high, thickly clothed with long, narrow, pointed tubercles, the bases of which are set in white wool, whilst the apices are crowned with tiny stars of white silky spines; more like the pappus of a Composite than the spines usually found on Cactuses.  A healthy plant has a very pretty and silky appearance which cannot well be described.  The flowers are small and unattractive; they are succeeded by the red fruits, which remain on the plant a long time, and add to its beauty.  Native country, Mexico.  Introduced 1838.  Should be grown in a greenhouse where frost is excluded, and where there is plenty of sunlight at all times.  It is easily increased, either from seeds or by means of the offsets developed at the base of old stems.

M. semperviva (ever-living); Fig. 70.—­Stem pear-shaped, 3 in. wide, the top slightly depressed.  Tubercles conical, 1/4 in. long, their bases set in a cushion of white wool, their tips bearing tiny tufts of wool, and four small spines, which fall away on the tubercles becoming ripe, leaving two short, diverging, central spines.  Flowers small, not ornamental, and scantily developed near the outside of the top.  Native of Mexico; in meadows and thickets near Zimapan, at 5000 ft. elevation.  It thrives with us when grown in a frame in summer, and wintered in a cool greenhouse or frame.

[Illustration:  Fig. 70.  Mamillaria semperviva.]

M. senilis (hoary).—­Stem about 3 in. high, spherical, unbranched, except when very old, when it becomes proliferous at the base; tubercles crowded, small, arranged spirally, and crowned with clusters of long, radiating spines, which are almost white, hair-like, and become thickly interwoven, as in the Old Man Cactus (Pilocereus senilis).  The central spine is black, and hooked at the tip.  Flowers on the top of the stem, near the centre; the petals toothed, spreading, and forming a deep cup, with a cluster of tall stamens standing erect in the middle; colour bright scarlet.  The flowers, which appear in summer, remain open about eight hours.  Native country unknown; cultivated in France in 1845.