The Yosemite National Park is perhaps the most delightful region in all the world for the study of plant life. The wide variety of conditions here found, ranging from the hot and desiccated slopes of the brush-clad foothills to the cold, bleak summits above timber line, the abode of glaciers and perpetual snow, gives to the flora an exceedingly diverse and interesting character. Innumerable springs, creeks, rivers, ponds, and lakes provide suitable habitats for moisture-loving plants. Rocky outcroppings, enormous cliffs, and gravelly ridges accommodate species adapted to such situations. The irregular topography yields southward facing slopes which receive the full effect of the sun's rays, as well as northward slopes where the sun's rays are little felt, where it is therefore cool, moist, and shady. The altitude ranges from two thousand five hundred feet in the foothill belt to thirteen thousand and ninety feet along the crest of the Sierra Nevada. All of these factors conspire to produce a remarkably varied and interesting vegetation. The richness of this flora is indicated by the nine hundred and fifty-five species and varieties here described. The total number represented in the Yosemite National Park is considerably greater, since the grasses, sedges, and rushes are here omitted. Including an estimate for these, it is safe to assume that the number of species and varieties of flowering plants and ferns to be found within the one thousand one hundred and twenty-four square miles of the park is not less than about one thousand two hundred. ("A Yosemite Flora," by Harvey Monroe Hall and Carlotta Case Hall.) 4. THE REALM OF FALLING WATER The Yosemite National Park is enlivened and splendidly enriched with mountain-high waterfalls and with wildly coasting and cascading streams. These world-famous falls gain an added attractiveness through the magnificence of the walls over which they plunge. In places the walls, clean-cut and smooth, rise sheer for more than one thousand feet. Here and there the line of a wall is broken with a vast niche or columnar buttress. A number of mountain streams and rivers in the Yosemite deliberately make their way to the brink of a vast gorge that has its brow in the sky, and there, in full self-control, they plunge over. Jutting rocks, and smooth steep inclines throw streams into wild, uncontrolled excitement. But where a vertical river drops its fluttering current against a magnificent mountain-wall, everything is harmonious and controlled, and the stream appears to have the sublime composure of a Big Tree. In a stream-channel water goes forward with crowding intermittent rushes. These, in plunging over a brink, break up into numerous closely falling rockets or comet-like masses, each tailed with spray. These in turn separate and divide into other such masses, with spray and water-dust.