(Greek, spine and cactus). Cac-tacese. A very large group of globular, strongly ribbed, and strongly spiny cacti, growing from the United States to South America, particularly abundant in Mexico.

Sometimes these cacti become very short-cylindrical; occasionally the ribs are broken up into tubercles which resemble those of Mammillaria; and rarely spines are entirely wanting: the flowers usually appear just above the young spine-bearing areas, but sometimes they are farther removed, and occasionally they are in the axil of a tubercle; the ovary bears scales which are naked or woolly in the axils, and the fruit is either succulent or dry. - The genus is well developed within the U. S., about 40 species having been recognized, but its extreme northern limit is the southern borders of Colo., Utah, and Nev., apparently having spread from the great arid plateau regions of Mex. proper and Low. Calif. The genus extends throughout Mex. but is not found in Cent. Amer. It is well represented, however, in the drier regions of S. Amer. Echinocactus and Mammillaria are distinguished chiefly by the way in which the flowers are borne, - terminal on the tubercles in the former, and axillary to tubercles in the latter. In external appearance they are very similar. The genus Astrophytum is here included, although it seems to be very different from the typical forms of Echinocactus and should doubtless be kept distinct.

It is impossible to identify with certainty all of the specific names found in trade catalogues, but the following synopsis contains the greater part of them. In all cases the original descriptions have been consulted, and in some cases it is certain that a name originally applied to one form has been shifted to another. The following synopsis may be useful, therefore, in checking up the proper application of names, but it may thus leave some of the common species of the trade unaccounted for. No attempt is made to group the species according to relationships, but a more easily handled artificial arrangement, chiefly based upon spine characters, is used. It must be remembered that the species are exceedingly variable, especially under cultivation, and large allowance must be made for the characters given in the key and in the specific descriptions.

Unlike most globular forms of cacti, echinocacti do not readily produce offsets; consequently they must be propagated by seeds if one wishes to increase these plants in quantity. Seeds of echinocactus, and, in fact, most cacti, will germinate as freely as seeds of other plants, provided they have been allowed to ripen properly before gathering and carefully dried afterward. The months of May and June have been found to be by far the most favorable for germination. Seeds of echinocactus will then germinate in five or six days, while during the winter months it takes almost as many weeks. Opuntias will germinate in even less than six days; they germinate most readily of all the Cactaceae, and grow the fastest afterward, while mammillarias are the slowest to germinate and grow the slowest afterward. - The seeds should be sown in well-drained 4-inch pots in a finely sifted mixture of one part leaf-mold, one part loam and one part charcoal dust and silver sand. The surface should be made very smooth, and the seeds pressed lightly into the soil with the bottom of a flower-pot and then covered with about 3/8 inch of fine silver sand.

This allows the seedlings to push through readily and prevents the soil from crusting on the surface of the pots, as they usually have to stay in their seedling pots at least one year. The pots should be placed in a greenhouse where they will receive plenty of light but not the direct sunlight, for, although cacti are natives of desert regions, the seedlings will roast if exposed to full sunlight under glass. For the first winter, at least, the seedlings should be kept in a temperature of not less than 60° and carefully looked over every day to ascertain the condition of the soil, for, although they should be kept on the dry side, they must never be allowed to become quite dry during the seedling stage. When about a year old they may be transplanted to shallow pans not more than 6 inches in diameter, and prepared with the same mixture as for seedling pots. These pans will be found better than small pots, because the soil may be kept more evenly moist and the seedlings do better in consequence. When grown from 2 to 3 inches in diameter, seedling echinocacti may be transferred to pots, using only sizes just large enough to accommodate them, as they make but few roots. Pot them in a mixture of two parts fibrous loam, one part leaf-mold and one part pounded brick and silver sand.

During the spring and summer months, established plants may be given a liberal supply of water, but must be studiously watered during the fall and winter months. - During the winter they should be given a light position in a dry greenhouse, with a night temperature of 45° to 50°, and a rise of 10° by day. For the summer, they may be either kept in an airy greenhouse or placed in some convenient position outside, plunging the pots in the soil or in some light non-conducting material. Some of the species will begin to blossom in May and others at intervals during the summer. The flowers vary considerably in size, and embrace a good range of color, from white to deep yellow, and from faintest purple to deep rose. They do not readily produce seed (in New England, at least) unless artificially pollinated. - Like most of the cactus family, the more cylindrical species will readily unite when grafted upon other kinds, not only in the same genus, but in other genera of Cactaceae, and for weak-growing species it may often be an advantage to graft upon some stronger-growing species. Cleistocaclus Baumannii (or C. colubrinus) makes an excellent stock to graft upon, choosing stock plants of reasonable size and height.