Everyone inquires about the century plant’s life expectancy. An insurance man might make an inference from the name. The plant is a big compact cluster or rosette of rigid, upward-pointing, spadelike leaves, each four or five inches in width and each tipped with a vicious, stout thorn. Year after year the plant just sits there by a boulder, unnoticed. I question whether anything alive on the desert has a better life expectancy. As far as my observations go, it has no diseases. It is invincible to drouth. Freezing does not harm it, and fire cannot burn it—although a yucca even when green will flame up like a torch. No hungry old cow can crop it, and no rodent gnaws it, at least not enough to do harm. And since the Indians have gone on reservations, no human uses it. So it stays there. In fact, nothing less than a caterpillar can leave a dent on it—not, of course, the caterpillar that eats young tomato plants, but the Caterpillar that pulls heavy road machinery. The plant just does not die before maturity, it would seem. A remarkable organism, indeed! But after many, many years, depending on the amount of moisture it receives, it makes up its mind to flower. In one tremendous effort, it shoots up a twelve-foot flower stalk at the rate of several inches a day. The blossoming is a final, dramatic, beautiful gesture, for by the time the flowers have withered, the great tenacious plant has turned to a ghastly purple and is dead. On the high slopes where the last yuccas end and only a few junipers remain in the race for survival, the yellow pines come in to mark off what is called the Transition Zone. The pines need no description, no printed promotion. The traveler, any traveler, can appreciate them although he might not be stirred to the slightest interest by the lovely yuccas. Since the beginning of time, the pines, fragrant, cheerful, companionable, have been man’s best friend. Among the ponderosa pines takes place most of the hunting, most of the camping, much of the picnicking. There is no danger that the tourist will overlook the pine belt and the pines for they are probably the most numerous tree in New Mexico. [Illustration: Piñon needles] Above them, the classifications are less clearly defined and ecologists are less inclined to agree on zonation. The Canadian Zone, if we settle on that name, occurs only in small areas on the map, and most of them north of Santa Fe. These are high ridges and island peaks that tower high enough to tempt the Engelmann spruces. Yet some of these islands occur as far south as the Mogollon Mountains and thus bring Canadian Zone scenes almost to the Mexican border. For hardy ecologists who want to explore high ridges and horns of bare stone which rise as clean as a hound’s tooth clear up into the Arctic-alpine Zone, it is necessary to enter Colorado.