M. elegans (elegant).—­A small species, grown only for the prettiness of its stem, flowers rarely, if ever, being borne by it under cultivation.  The stem is 2 in. high and wide, globose, with small conical tubercles, which, when young, are woolly at the tips.  Spines short and slender, about twenty, arranged in a star on each tubercle, with four central ones a little longer than those which surround them; the colour of the spines is whitish, with brown tips.  Native country Mexico, on high exposed hills; in this country it requires greenhouse treatment.  Introduced about 1850.

M. elephantidens (elephant’s-tooth); Fig. 60.—­One of the largest and most remarkable of all garden Mamillarias.  Stem globose, depressed, 6 in. to 8 in. in diameter, and bright shining green.  Tubercles smooth, round, 11/2 in. long, furrowed across the top, which is at first filled with wool, but when old is naked.  At the base of the tubercles there is a dense tuft of white wool, and springing from the furrows are eight radiating recurved spines, and three short central ones, all strong, stiff, and ivory-white, tipped with brown.  The flowers are 3 in. wide, and are composed of a circle of violet-coloured sepals, with white margins, and a second circle of petals which are bright rose, pale purple at the base, a line of the same colour extending all down the middle.  The stamens are numerous, with long purple filaments and yellow anthers, and the pistil is stout, erect, projecting above the stamens, with a radiating stigma.  Flowers in autumn; native country, Paraguay.  Under cultivation, it grows quicker than is usual with plants of this genus, and it is also exceptional in the regular and abundant production of its flowers.  It has been a rarity in European collections for many years, and, although easily grown, it is often killed through wrong treatment.  A cool greenhouse or sunny frame in summer, plenty of water whilst growth is active, and a light, well-drained soil, suit it best; whilst during winter it must be kept perfectly dry, and protected only from frost.  In a tropical house, it is invariably sickly, and altogether unsatisfactory.

[Illustration:  Fig. 60.  Mamillaria ELIPHANTIDENS.]

M. elongata (elongated).—­A small, cushion-like kind, with the stems in tufts, owing to their producing offsets freely from the base, the tallest of them being about as high and as thick as a man’s thumb.  The tubercles are short, crowded, and hidden under the star-clusters of reddish-yellow spines.  There are no central spines in this kind.  The flowers are produced in the axils of the tubercles from all parts of the stem, a large tuft of stems being thickly studded with circles of tawny yellow petals, which are only about 1/2 in. long.  The berries are bright coral-red, and about the size of a date stone.  There are several varieties of this species, under the names of intertexta, rufescens, rutila, subcrocea, and supertexta.  These differ only slightly either in the length or thickness of the stems or in the colour of the spines.  All of them may be grown in a cold frame, or in a window where the sun can shine upon them; or they may be grown along with tropical kinds.  For small cases in windows, these little Thimble Cactuses are amongst the most suitable.  They are natives of high mountains in Mexico, and have been cultivated in Europe over forty years.