And now we will pause in our trip across Cactus Land to take up the many peculiar features which characterize and differentiate these odd desert plants, and to tell of those individual and unique growths, the terrible swordlike thorns of the strange Fantastic Clan.

PECULIARITIES

Cacti are not closely related to any other family of plants, and there is no certainty as to which group of plants they developed from. Their immediate ancestors perhaps have disappeared in the hazy past. They stand, therefore, alone. In this respect few other plants resemble them; only one or two other families, for instance the Ocotillos or FouquieriaceÆ, are in a like position.

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.

A new and handsome little strawberry cactus, named in honor of Frances Bonker for her writings depicting the beauty and charm of the desert land.

SPINES AND FLOWERS

The spines of cacti are ever an interesting subject for study, and the very name “cactus” is suggestive of thorns. It is generally known that cactus spines develop from their bases and that they are impregnated with resin or a resinlike substance, while the spines of nearly all other plants (as for instance the plum) grow from their tips and are not resinous in character. A young growing cactus spine has a very soft yielding base while the tip is hard and sharp, and the sides retrorsely barbed. Because of their resinous nature the thorns persist on the desert long after the cactus body has disappeared, and often fragments of the thick cuticle remain with them, still firm, sharp and translucent. Such spines about a spot where a noble Sahuaro or Giant Cactus has fallen and gone back to Nature as dust may persist for a long period unchanged, without crumbling or otherwise disintegrating; this is true also of those of the bisnaga or barrel cactus. Thorns grow on the Giant Cacti for a hundred, even two hundred years, unalterable, sharp and hard and dangerous. Some species of cactus have as many as three kinds of spines: centrals, the inner thorns, usually the largest and stoutest; radials, the outer spines; and what are termed “bristles” but are more accurately described as “antennalike” spines. In some groups, as the bisnaga, the spines are cross-ridged or marked transversely, with the tips smooth, straight, or hooked. Many cactus spines are marked with brilliant colorings, and some are transversely banded with bright variegated “zones” of color. When held to the light they are translucent and show beautiful colorings: red, orange, yellow, brown, and purple. Generally cactus spines are glabrous, that is, smooth and without hairs, but the spines of some cacti are densely fine-hairy or distinctly hairy; and this can be seen easily with a pocket lens or the unaided eye: their pubescence commonly produces a grayish layer overlying the true color of the spines beneath. The thorns of Cholla differ from those of other cacti in that they are covered with sheaths which can be removed very easily, and then are not replaced. The significance of these sheaths is not clear, except that they help form a barrier against the intense heat of the sun and the burning desert sands.

We find, too, that the cacti with most pronounced thorny growth live in the hottest parts of the desert, where the thermometer often registers 130° Fahrenheit during the long summer days and sometimes up to 150°! Their dense layer of spines becomes a shield of lacework, protecting the plants by cutting off over twenty per cent of the light, and reducing the terrible heat by raising the humidity within the network of spines, which in turn reduces evaporation from the plant. If it were not for their thorns and sheaths cacti would be scalded by the burning temperatures of even one summer day in the great desert amphitheater of the sun. Being resinous, cactus thorns are very inflammable, and if ignited they all burn to a cinder before the fire ceases, for one cluster of spines will set others aflame and so the fire sweeps over the entire plant, rapidly changing the beautifully colored, symmetrical and translucent spines into ugly charred masses.

The cactus is encased in a thick cuticle which is continuous over the whole surface of the plant, except at the numerous, small, rounded or oval areas of growth called areolas. In the cactus all growth, of leaves, spines, spicules, flowers, and even roots (in the case of cuttings) and branches, takes place from these areolas, which are truly areas or centers of growth; and if all these areolas are cut away on the stem and its tip cut off, the plant ceases to grow and dies. Spines are generally understood to represent branches, since they grow from the tissues of the plant under the epidermis and not from the epidermis. The inordinate multiplication of spines in cacti is not well understood by botanists. Some cacti add thorns to their spine clusters in the areolas each year, and thus in time the cluster may come to have as many as fifty or even a hundred spines on old stems and large branches. Occasionally cactus spines replace themselves in areolas after the former thorns have been destroyed or burned off. The thorns of some cacti may grow as long as six inches and even longer, and as broad as one-fourth inch at their bases. After they complete their growth toward the close of the season and the bases become hard and firm, they do not elongate farther nor make further growth.

The flowers of cacti are generally large and showy and are quite responsive to light in their opening and closing. They have many stamens, from thirty or fifty to as many as three thousand in the Giant Cactus. This development of stamens is rare among flowering plants, and is due to a splitting process that takes place early in the development of the stamens of the embryo flower. The stamens of many cacti are sensitive to touch and when being worked by insects for pollen are constantly moving backward and forward. Cactus flowers differ also from nearly all other flowers in the number of sepals and petals, which is variable and relatively large, and in the fact that their sepals and petals are not distinct in character. Rather there is a gradual transition between the bracts of the ovary, if such are present, and the sepals; and likewise a gradual gradation in form, color, and size between the sepals and petals. There are usually several whorls or circles of petals in the flower; commonly such flowers are spoken of as being double.