M. pycnacantha (densely spined); Bot.  Mag. 3972.—­The name for this kind is rather misleading, the spines being both fewer and less conspicuous than in many other species of Mamillaria.  Stem about 6 in. high, nearly globose; tubercles—­rather large, swollen, with tufts of short white wool in their axils, and stellate clusters of spines springing from disks of white wool on the top.  The spines are 1/2 in. long, slightly recurved, flattened, and pale brown.  Flowers large, clustered on the top of the stem, about half a dozen opening together; width 2 in.; petals numerous, narrow, toothed at the tips, spreading; colour a deep sulphur-yellow, anthers orange.  Native of Oaxaca, Mexico.  Flowering season, July.  Introduced 1840.  This is a beautiful flowering plant, more like an Echinocactus than a Mamillaria.  It should be grown in a warm greenhouse all the year round.  Old stems develop offsets from the base, by which the species may be multiplied.

M. sanguinea (bloody); Fig. 68.—­This is closely related to M. bicolor, but differs in having an unbranched stem and numerous richly-coloured flowers.  The stem is stout, 6 in. high, and 4 in. through; tubercles crowded, short, bearing stellate tufts of shortish spines, and projecting longer ones, all being bristly and pale yellow, except those on the youngest tubercles, which are golden.  The flowers are borne in a crowded circle on the top of the stem, just outside the cluster of young yellow spines, a strong plant having about forty flowers open together.  Each flower is about 1/2 in. long and wide, and coloured bright crimson, with yellow anthers.  Native of Mexico.  Flowers in June.  It should be grown along with M. bicolor.  The plant figured is a young one, showing the spines much longer than is usual on mature specimens.

[Illustration:  Fig. 68.  Mamillaria sanguinea.]

M. Scheerii (Scheer’s).—­Stem 7 in. high, and 5 in. in diameter at the base; tubercles large, swollen, somewhat flattened, pale green, watery, woolly in the axils, the tops crowned with about a dozen brown spines, 1 in. long, one central, the others radial.  Flowers terminal, erect, with several whorls of spreading, recurved petals, the lower ones tinged with crimson, the upper pale yellow, and forming a shallow cup, 2 in. across; anthers forming a compact sheaf in the centre.  Flowers in summer.  This distinct and very pretty species was introduced many years ago from Mexico, where it was discovered in 1845 by a Mr. Potts, to whose love for these plants we are indebted for a great many choice kinds collected and sent to England by him.  It grows naturally in a red, sandy loam, and under cultivation requires warm-house treatment, except during the autumn, when it may be placed in a frame and exposed to full sunshine and plenty of air.