Cacti are generally thought of as limited to North and South America and the outlying islands. However, about eleven species of one genus, Rhipsalis, grow, apparently native, in South Africa, Madagascar, and Ceylon, though these are identical with the same species growing in South America. There is a strong belief that these species were distributed in Africa by birds eating their ripe fruit in South America and then flying across the ocean to Africa, and there dropping the seeds, which germinated and grew into plants on another continent. The most widely distributed of the various groups of cacti is the prickly pear group of the genus Opuntia. The prickly pears grow wild from Argentina through Central America, Mexico, and the United States to British Columbia, within four or five hundred miles of the Arctic Circle. Prickly pears may be regarded as the advance guard of the cactus invasion of the United States from Mexico, and there are nearly as many kinds in our country as in Mexico. Prickly pears are most abundant in the temperate zones; the species grow larger in tropical parts than in cooler temperate regions. All told, there are more than twelve hundred species or kinds of cacti, of which about two hundred twenty-five occur in the United States and the rest in Mexico, Central America, South America and outlying islands. Of the two hundred twenty-five species occurring in the United States, about one hundred are native of Arizona, the premier cactus state, and nearly two hundred grow in the four southwestern states, California, Arizona, New Mexico, and Texas, with a few in Nevada and Utah. Arizona contains almost one-tenth of the cacti of the entire earth. Our four southwestern states together with Mexico constitute the great cactus area of the world, not alone in numbers but in variety and weirdness of types, containing many of the most peculiar and fantastic forms of these grotesque plants. Doubtless because the cacti are such odd, weird, fantastic growths, they have been popular with mankind since the earliest times. To-day forty or fifty species are known only in cultivation; and they have been under culture so long that their native habitats and original distribution have been forgotten, and are no longer known. This is due largely to the fact that several very popular species have been dug up and removed from their own haunts to cultivated lands, or planted in gardens to such an extent that the last specimens have been taken and they no longer grow wild or under natural conditions. This uprooting is taking place continuously, doubtless much faster now than formerly, and in future we shall have many additional instances to record, as it is quite likely that new species are originating under experimentation through careful selection and ingenious plant breeding. [Illustration: SHORT SPINED STRAWBERRY CACTUS (Echinocereus Bonkeræ)]