There is also the _palo verde_, named for its color, with its bright, vivid green leaf, twig, and bark, and its pretty yellow blossoms, making a beautiful contrast with the more somber green of other trees. Occasionally great rows of cottonwoods (the _alamo_ of the Mexicans) show the line of water courses, while a number of shrubs covered with blossoms are seen, apparently half tree, half cactus, so thick are their brambles and thorns. But as to cactus! There are five hundred species in America, of which Mexico has a large plurality, and the majority of these can be found along this end of the Sonora railway. There is the giant pitahaya, sometimes with a dozen arms, each as big as an ordinary tree, and from thirty to forty feet in height. Each arm has a score of pulpy ribs along its sides, and each rib has a button of thorns every inch along its length, each button having twenty or twenty-four great thorns sticking from it. I was told that when a hunter is sorely pressed by peccaries, if he will climb a pitahaya about ten feet, the thorns are so thick and terrible in their effect that the peccaries will not dare to follow him, hardy and venturesome as they are. Then there is the choya or cholla cactus, about as high as one's waist. You can go around a pitahaya as you would a tree, but when you find a field of chopalla (field of choyas) you might as well try to go around the atmosphere to get to a given point. The cholla will lean over until it breaks its back trying to get in your way, so that it can dart a dozen or two spines into your flesh. They are the worst of all; I could use almost as much of my readers' time in describing different cactuses as I used of my own in picking them out of my flesh after the peccary hunt was over, but I forbear. [Illustration: A MEXICAN CACTUS]