They were too thirsty to pause to make inquiry as to the cause of this wholesale fatality, and hurried on to the spring to cool their parched tongues. The leader of the party, however, was suspicious and insisted that no one should take more than a few drops of the water at that time. His caution proved their salvation, for within a few minutes after drinking of the water all were taken violently ill. The spring was a natural arsenic fountain. As soon as the party was able to travel the journey was resumed and Timber Mountain was reached in safety. The guide carried away some of the water for analysis and thus learned of the properties of the spring. Later, he returned and set up a sign to inform travelers of the dangerous character of the water. CHAPTER III CURIOUS PLANTS WHICH LIVE IN THE DESERT In the mystic mid-region grows vegetation as weird and wonderful as the region which it inhabits. The Mojave yucca (_clistoyucca arborescens_) is a strange freak of vegetation found nowhere else in the world. The palo-verde stands grim and sentinel-like, along the banks of the Colorado River which skirts the deserts, an evergreen but leafless tree with curious branches which cross and recross each other, forming a perfect network of green vegetation. Cacti in innumerable variety abound in certain portions of the deserts, from the tiny prickly balls covered with long gray hairs to the giant sahuaro which attains a height of fifty feet. In some places the deer-bush thrives: this plant is so named because of the resemblance borne by its branches to the horns of a deer. There are also sage, mesquite, chaparral, and greasewood, and numbers of other peculiar species of plants. [Illustration: SAHUARO, OR GIANT CACTUS From photograph by C. C. Pierce & Co.] Cacti are the most numerous of the species of vegetable life. The several varieties all have their uses to those versed in the lore of the desert. In them the Indians, who make the desert their home, find food, drink, raiment, and shelter. This is particularly true of the _cereus giganteus_, which is abundant in the arid regions of Southern Arizona, New Mexico, Texas, and Mexico. This plant grows, in many cases, to a height of fifty feet. In some sections it grows so thickly that several hundred plants are found on a single acre. The plant consists of a main trunk which rises to a height of from ten to twenty feet, and then branches into two, three, or several columns, which grow upright several feet. The main trunk and branches are ribbed, and these ribs are thickly studded with clusters of heavy spines, which if lighted will burn readily, the flame running up the ribbed columns, seeking and burning all the spines thereon. This fact has given rise to the name of "Arizona candle" which is often applied to the giant cactus.