"Studies perfect nature," Bacon said. "Nature follows art" to the extent that most of us see principally what our attention has been called to. I might never have noticed rose-purple snow between shadows if I had not seen a picture of that kind of snow. I had thought white the only natural color of snow. I cannot think of yew trees, which I have never seen, without thinking of Wordsworth's poem on three yew trees. Nobody has written a memorable poem on the mesquite. Yet the mesquite has entered into the social, economic, and aesthetic life of the land; it has made history and has been painted by artists. In the homely chronicles of the Southwest its thorns stick, its roots burn into bright coals, its trunks make fence posts, its lovely leaves wave. To live beside this beautiful, often pernicious, always interesting and highly characteristic tree--or bush--and to know nothing of its significance is to be cheated out of a part of life. It is but one of a thousand factors peculiar to the Southwest and to the land's cultural inheritance. For a long time, as he tells in his _Narrative_, Cabeza de Vaca was a kind of prisoner to coastal Indians of Texas. Annually, during the season when prickly pear apples (_tunas_, or Indian figs, as they are called in books) were ripe, these Indians would go upland to feed on the fruit. During his sojourn with them Cabeza de Vaca went along. He describes how the Indians would dig a hole in the ground, squeeze the fruit out of _tunas_ into the hole, and then swill up big drinks of it. Long ago the Indians vanished, but prickly pears still flourish over millions of acres of land. The prickly pear is one of the characteristic growths of the Southwest. Strangers look at it and regard it as odd. Painters look at it in bloom or in fruit and strive to capture the colors. During the droughts ranchmen singe the thorns off its leaves, using a flame-throwing machine, easily portable by a man on foot, fed from a small gasoline tank. From Central Texas on down into Central America prickly pear acts as host for the infinitesimal insect called cochineal, which supplied the famous dyes of Aztec civilization. A long essay might be written on prickly pear. It weaves in and out of many chronicles of the Southwest. A. J. Sowell, one of the best chroniclers of Texas pioneer life, tells in his life of Bigfoot Wallace how that picturesque ranger captain once took one of his wounded men away from an army surgeon because the surgeon would not apply prickly pear poultices to the wound. In _Rangers and Pioneers of Texas_, Sowell narrates how rattlesnakes were so large and numerous in a great prickly pear flat out from the Nueces River that rangers pursuing bandits had to turn back. Nobody has written a better description of a prickly pear flat than O. Henry in his story of "The Caballero's Way."