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other delicate species, all plants requiring continuous moisture, while even the familiar mullein and Jamestown weed occur. This flora of the valleys is of interest, inasmuch as it is a modified representative of that of the great Atlantic timber belt, occurring as an isolated outlier in the semiarid region, preserved and nurtured in these valleys by the presence (due to geologic causes) of water and soil.

While the valleys support this modified flora of the humid region, the rocky slopes of the breaks between the streams and the summit present another group of vegetation shrubby trees which prefer the crevices of rocks, or small scrubby plants which develop large, strong, and hearty roots, out of proportion to the size of the growth above ground. These plants are found along the ledges of limestone wherever their roots can find a hold, or on the almost soilless outcrop of the interstratified chalky marls. Among them are dwarf oaks, the pinon Sopliora, and mountain juniper, which seem to prefer to follow the ledges of loosely jointed rock, besides many coriaceous perennials, including the agarita (Berberis) and the eastern yucca. There are also many small species of Compositor, Liliaceae, the wild poppy (Argemone mexicana), and other plants growing on these slopes.

West of the Frio, in the breaks of the south end of the Edwards Plateau, where the rocks are hotter and more arid than to the eastward, the remarkable and unique resurrection flora of the limestone mountains of Mexico is found. This is characterized by plants growing upon the hot and sterile rocks, and adapted to irregular rainfall, long drought, and scarcity of soil by their thick, coriaceous parts, which ordinarily look dry and dead, but which rapidly unfold and revive after a rain, taking advantage of every drop of rainfall in order to store sufficient moisture to enable them to survive the long periods of intervening drought. Even the ferns, mosses, selaginellas, and kindred plants, which ordinarily constitute our ideals of delicate and tender herbage, have in this region a thick, leathery texture. On the almost barren surface of these rocks grows the melon shaped, edible cactus the devil's pincushion.

Here also, for the first time in proceeding westward across Texas or northward across the Rio Grande Plain from Mexico, one meets the peculiar plants (agaves and yuccas) which become so marked a feature farther westward, the serrated sotol, with its flower stalk rising to a height of 15 feet; the dagger like lechuguilla or ixtle plant, and several species of yucca not seen farther eastward.

The flora of the summit of the plateau is radically different from that of the breaks or of the valleys. All trace of shrubs or trees disappears, save here and there a patch of shin oaks and dwarf evergreens, and in time of verdure the eye beholds apparently a never ending sea of grass, "

In the lower slopes, around the headwaters of the Frio (Frio water hole), the writers last year discovered a large area of the edible Berberis swaseyi Buckley, a species which Coulter says in his Flora of West Texas is known only from the canyons of the Pedernalis. The fruit of this plant is a large edible berry well worthy of cultivation. We have never seen it elsewhere.