This chapter treats of the _Opuntia_ genus of Cactaceæ, the well known group of Prickly Pears whose flower colorings are remembered as being so exquisite and delicate, so vivid and attractive both near and afar, the lovely tints and hues so well graduated from the bases of the petals to their tips and so symmetrical of distribution, that attention is at once focused upon them. There are about two hundred sixty species of the _Opuntia_, of which eighty-eight are in the United States, eighty-seven in Mexico, and the remainder in South America and the outlying islands. The genus _Opuntia_ includes not only the beautiful Prickly Pear but also the familiar Cholla, that tall, stately, antlered plant of the desert domain which frowns at you from along the highway as you approach our no man’s land from almost any direction. Starting on a fourth trek into the habitats of cactus plants early in May, we shall look for only the colorful Prickly Pears, characterized by their large pear-shaped joints, the “flapjacks” of the desert; characterized also by their large flaming orange and yellow, or occasionally rich purple and red blossoms, which open for only a short time during the day and close when the shadows of the sun begin to bathe the hills in orange and purples as the desert sunset approaches. In a few cases they unfold for a short time the following day, but most bloom for but the one period of five to seven hours or so. Commonly the blossoms change from yellow when they open to orange in the afternoon, and in some species to red-orange. It is also noted that when the flowers unfold for a second day, their bright colorings deepen and darken in orange or red. We find that the clan of the Prickly Pear nearly always have thorns different from those of most other groups of Cactaceæ in that they are only of one kind, though the sizes may vary. In the genus of _Opuntia_ there are no radial nor central spines; the thorns are merely spines in the full sense of the word. We note that the Prickly Pear is really a shrub with many stems branching from the base, and that their pear-shaped joints are in reality stems or branches and are not just leaves as many suppose; the true leaves being very small and scalelike and disappearing after a short time, withering away and falling off. The species grow readily from these pearlike joints, and this is a common method of propagating _Opuntia_. They will also grow from seeds, but these develop very slowly and require a long time in the ground before they germinate. Papago Fruit Cactus (_Opuntia Blakeana_) _Southern Arizona_