The genus is a large one with over 200 species. They are mostly natives of Mexico and are favoured plants in collections. Many are easily grown fromand, although the are not large, a number appear in a ring around the top of the plant, and usually last for some days. Most species prefer full sunshine, but there are a few that grow best in half shade, especially during the bright days of summer. Besides their pretty flowers, they produce fruits, mostly red.
elongata. W. Mexico. Forms clusters with which are generally cylindrical and erect, but sometimes prostrate. This species is very and popular in collections. There are a number of varieties, all of which are worth while growing, particularly var. echinata, var. rufocrocea, and var. stella-aurata.
microhelia. Mexico. A very beautiful species preferring full sunshine. The is solitary or sprouting, with short tubercles. Radial spines number about 50, central spines 1 to 4. The flowers are creamy-white.
Mammillaria plumosa. N. Mexico. A beautiful species, forming clusters entirely covered with feathery spines. The flowers are white, with a brown or reddish mid-rib. The plant is of easy cultivation in full sunshine. Watering should be frequent in the growing season, but in winter the plant should be kept dry.
Mammillaria kewensis. Mexico. An interesting species having 5 or 6 brown radial spines fixed in star fashion on the tubercles, there being no central spine. The flowers are purple.
Mammillaria Heyderi. N. Mexico, Texas. An attractive plant with a flattened hemispherical, and conical, angular tubercles. The bristle-like radial spines are white with brown tips and number 20, the outer ones long. There is 1 central spine. Flowers red, with dark central bands.
Mammillaria camptotricha. Mexico. Spherical with dark green stems, forming large clumps. Spines number 4 or 5. The outer petals of the flowers are greenish, the inner petals white. The plant is easily cultivated and deservedly popular.
Mammillaria Parkinsonii. Central Mexico. The sea-green stems are somewhat 8S compressed, conical to cylindrical in shape. Radial spines number 20 to 30, with 2 central spines, tipped with dark brown. The flowers are small and yellowish. A very beautiful plant, often seen in collections.
Mamtnillaria hahniana. Mexico. One of the most beautiful of the, it has a globular stem, rather flattened on top, with silky white hairs which give the plant a singular appearance. Radial spines number about 30; there are 2 central spines, which are straight and erect. The crimson flowers are arranged in a ring around the top of the plant.
Mammillaria rhodantha. Mexico. The species has a dark green cylindrical stem, which forms large clumps with age. Radial spines number 16 to 20; central spines 4 to 6. The flowers are numerous, the outer petals reddish-brown with a white margin, the inner petals carmine-red. There are numerous beautiful varieties, and all are of easy cultivation.
Mammillaria celsiana. Mexico. The stem is solitary, globular to cylindrical, rather flat on top and well furnished with white wool. Radial spines number 20 to 26, central spines 4. The flowers are produced in a ring at the top of the plant, the outer petals reddish-brown, the inner petals pink to carmine. A very lovely species thriving best in half shade.
Mammillaria bombycina. Mexico. The stem is globular, becoming cylindrical with age, with blunt tubercles arranged in spirals, and conspicuous for their white wool. Radial spines number 30 to 40, central spines 4. The flowers are clear red.
Mammillaria pusilla. More commonly named M. prolifera. Clusters freely, making a fine pot plant. The dark green stems, soft in texture, are globular or short and cylindrical, with tubercles closely set in spirals of 5 and 8. Central spines number 5 to 9, with up to 40 radial spines. The outer petals of the flowers are greenish-yellow, while the inner petals are broader and paler. The following varieties are in cultivation: var. haitensis, var. texana, var. multiceps.
Mammillaria saetigera. A globose species with the apex somewhat sunken. The tubercles are loosely arranged in 13 and 21 spirals, and glossy dark green. The areoles are elliptical with white wool only in the youngest. The axils have white wool, and also white bristles, especially in the lower part of the plant. Central spines number 2, radial spines 15 to 20. The flowers are white with a rose mid-stripe, the inner petals being darker.
Mammillaria gracilis. Forms clusters with cylindrical stems of a fresh green. The areoles are slightly woolly and bear 12 to 14 radial spines, which are yellowish-white at first, passing to white, stiff, and radiating star-like over the tubercles; central spines number 3 to 5. The flowers are yellowish-white. Two varieties are in cultivation: var. fragilis and var. pulchella.
Mammillaria microcarpa. One of the best of the Mammillarias. The stem is solitary, globose to cylindrical, rounded at the apex, with the tubercles arranged in 13 and 21 spirals. The stem is firm in texture, becoming corky with age, and a dark greyish-green. Central spines number 1 to 3, radial spines 20 to 30, and are white to dark yellow with a brown tip. The outer petals of the flowers are greenish with a tan mid-stripe, darker at the tip, and have pale green margins, with a tinge of pink; the inner petals are pink, with darker mid-stripe and very pale margins.
Other species to be recommended are: M. erythro-sperma, M. Wildii, M. kunzeana, M. Schelhasei, M. decipiens, M. Candida.