Colorado's great diversity of flowers, shrubs, and trees is attributable to the climatic conditions that prevail at widely different altitudes. Each thousand feet in altitude represents an approximate difference of three degrees in temperature; the range in temperature found in a thirty-mile journey from the plains to the top of the Continental Divide is greater than that ordinarily experienced in traveling a thousand miles from north to south. For this reason few parts of the world are more interesting biologically than the Rocky Mountains.

To the amateur botanist Colorado offers exciting exploration in regions where new species are constantly being discovered; the professional student finds here an almost limitless opportunity for intensive study and research. To the wayfarer unacquainted with technical names or scientific data but appreciative of stately trees and beautiful flowers, the landscape presents colorful and beautiful scenes with the changing seasons.

The first professional to "botanize" in what is now Colorado was Edwin James, historian and naturalist of Major Long's expedition of 1819-20, which traveled southward from the South Platte Valley along the mountains. The wild mock orange has been named Jarnesia, or Edwinia, in his honor. Fremont's expeditions in 1842-45 were accompanied by botanists John Torrey and Asa Gray; the latter's papers appeared in official documents and in the Americal Journal of Science. Between 1860 and 1870 local specimens were collected by Charles C. Parry, for whom the Parry primrose was named. Among other naturalists of this period was George Engelmann of St. Louis, for whom the Engelmann spruce was named.

Colorado flora, according to the best authority, is distributed among five zones, each with its more or less distinct characteristics. The semiarid plains zone ends at an altitude of 6,000 feet; the foothill zone lies between 6,000 and 8,000 feet; the montane zone extends to 10,000 feet, and the subalpine to 11,500 feet, with the true alpine zone above it.

Although at first sight the plains seem to be merely a brown or tawny expanse of buffalo and grama grass, closer observation reveals a surprising variety of plant forms, usually low and sparse, but intensely colorful. Scientists have recorded 2,989 different varieties of wild flowers in and near the foothills, 500 of which are peculiar to the plains alone. Climatic conditions in this section have made the cultivation of seed flowers an important enterprise in the river bottoms.

In the spring, before sun and wind have dried the soil, prairie flowers are numerous—the early-blooming sand lily, the evening primrose with blossoms shading from cream to rose pink, strong-scented yarrow, coral-colored wild geranium, yellow and orange buttercups, Colorado bee plant, and the white star flower that blooms at dusk. At times the plains are covered with a mantle of wild dwarf marigolds. By midsummer, most of these flowers are gone, but a few linger in the river bottoms with wild iris and graceful cattails. Only the yellow sunflower and the purple-tasseled Scotch thistle flourish with undiminished vigor through the summer amid pigweed, shepherd's-purse, and Russian thistle, or tumbleweed. Another hardy plant is the devil's claw, the seeds of which are distributed by pronged seed pods which cling to every moving object that touches them. The ubiquitous loco weed, with violet, cream, or white flowers, is bitterly hated by cattlemen for its poisonous effect upon livestock.In drier regions the plains are carpeted with biennial burdock or cocklebur, Mexican sandbur with delicate yellow blossoms and villainous triangular thorns, prairie sandbur, silvery sage, and the mesquite shrub with its fragrant blooms and sugar-filled pods. Some plants in the arid regions, like the rose mallow and the purple-flowering bush morning glory, project their roots six to ten feet deep in search of water. Both on the eastern prairies and in the western mesa country grows the yucca, popularly known as soap weed, or Spanish bayonet, its great spike of creamy flowers projecting from a barricade of dagger-tipped leaves. With its deep-growing fibrous roots it flourishes on arid land. The four varieties native to the State were long used by Indians for many purposes; its tough leaf fibers were made into rope; the pods were ground into a flour; the roots, which lather freely in water, were used as a soap.

Colorado has twenty-four varieties of cacti, nineteen of which can be seen at the Colorado Museum of Natural History, Denver. The opuntia, or jointed cactus, assumes forms ranging from the flat-lobed prickly pear, blending all too well with the prairie sod, to the giant tree cactus, which attains a height of ten feet in Furnace and Blacksmith Canyons in the southern part of the State. The blossoms of the prairie cacti are usually yellow, although some are a deep silky red or hybrid orange. Southern Colorado produces a round-lobed pincushion cactus bearing pink, yellow, and deep wine-colored flowers. Peculiar to the Western Slope is the rose-colored prickly pear. The pods of the cactus are often fried, and its leaves are sometimes used in the manufacture of candy.

Buffalo bush, with silvery foliage and edible berries, nuttals, and round-leaf saltbush are among the chief shrubs of the plains. Rabbit-wood, a kind of sandalwood with greenish flowers and pulpy fruit, is common, as is the creosote bush, so named because its resinous foliage has a strong odor of creosote. Gray saltbush, or chico-brush—better known as greasewood—grows in alkaline soil and in the shale beds of the lower foothills. Thirty species of shrub willows border lowland streams and grow in marshy areas; many are highly ornamental and are sought in the spring for their silver catkins.

Native cottonwoods, esteemed by early settlers on the hot plains, have been largely replaced in the more populous areas with more desirable poplars, elms, maples, birches, and locusts, all transplanted. Often mistaken for a willow, the narrow-leaf cottonwood usually grows along the rivers at low altitudes. The lance-leaf variety is occasionally found near Colorado Springs and Fort Collins, and across the Divide at Montrose. As the plains rise toward the foothills, beaked hazel nut, mountain ash, green ash, Rocky Mountain maple, and box-elder become common; mountain and scrub oak grow along the streams, and dog birch flourishes in the marshes.

The Colorado oak occurs on both sides of the Continental Divide but prefers the rocky hillsides in the southern part of the State, as does the Norman tea fir with its slender loose-spreading limbs. The southern foothills are also noted for their thick growths of Rocky Mountain cedar, which grows in stunted shrub-like masses on otherwise almost sterile ridges. Desert juniper, rock pine, and manzanita are ubiquitous in southern Colorado, giving way to scrub juniper and trailing cedar in the north. Dense knotty pinon pines with low spreading dark branches are found from the Wyoming border to Mesa Verde National Park..

The foothill region is matted with berry shrubs: hackberry, Fendler's barberry, Fremont's barberry, snowberry, wolfberry, thimbleberry, Western buckberry, billberry, and coralberry. Currants, gooseberries, wild grapes, plums, strawberries, elderberries, Western chokeberries, and other edible wild fruits ripen in ravines and canyons. Turret plant, or deer's tongue; Oregon grape, an evergreen shrub with blue berries, often used in place of holly during the Christmas season ; kinnikinnick, known as bearberry in other parts of the country and used by the Western Indians as a substitute for tobacco, bearing delicate ivory-colored flowers in early spring and bright scarlet berries later—all grow thickly on the higher foothills. Yellow Johnny-jump-ups gleam in mossy crevices, and the hairy-stalked pasque flower raises its purple spikes from plains to alpine meadows.

Colorado lichens, often mistaken for moss, are among the most familiar flora of hill and mountain country. Lichens often encrust tree trunks and limbs but more generally cling to rocks in patches of pale green, yellow, gray, and brown. Dry air and scant moisture are unsuited to fern life, but thirty varieties of this plant have been collected within the State, chiefly from shadowed canyons and rocky crevices in the subalpine zone; the most common are the bracken, the lady fern, and the male fern.

The columbine, Colorado's official flower, reaches perfection in the cool shade of tall aspens but is found from the lower foothills to timberline. Its specific name coerulea means blue, but its sepals are sometimes purple, pale lavender, and even white. A companion flower, the wild yellow pea, often grows among columbine clusters.

Wild roses, ranging in color from almost pure white to deep red, scent the air of foothills and mountains during June and July. On the higher slopes bloom pale lavender Mariposa lilies, one of the best known of Colorado's wild flowers; here also occur mountain lilies, orange-red wood lilies, and maroon-centered gaillardia, intermingled with dwarf cornel, mountain rue, and wild four o'clock. Midsummer is the blooming season for rose and cream meadow lotus, azure-fringed gentians, and pink-and-white wood mint. Fragile Dutchman's pipe, the yellow dog's tooth violet, even occasionally the rare pink variety of the latter, mingle with purple woods violets and blue bells in secluded hollows, while the forest floor is dotted with yellow butterweed, tall bitter cress, purple monkshood, and chiming bells. Brown-eyed Susan, gay-plumed Indian paint brush, coral fox glove, delicate blue harebells, mountain forget-me-not, and mountain daisy spill over the slopes in a riot of color intensified later by pink eight-petaled dryads, asters, golden rod, and the single- and twin-flowered wintergreen.

The orchid family is represented by the golden lady slipper, the delicate little calypso, lady's tresses, and spiranthes, growing in mountain meadows and along streams. The coral-root orchid is frequent!) found in the woods, as are the peculiar pine drops of the Indian pipe family. In shaded marshes blossoms the little red elephant, originally discovered in Greenland; each flower on its spike resembles the head and trunk of a miniature elephant.

High in the mountains the white marsh marigold, yellow globe flowers, and the purple anemone, or wild crocus, push through the snowbanks in early spring and summer. Along streams fed by melting snows are the alpine primrose, the topaz monkey flower, the kings crown, and the rose crown. The alpine gold-flower is perhaps the most striking, and throughout July it carpets high mountain meadows with its vivid yellow. Dense matted clusters of fragrant brilliant-hued alpine flowers, seldom more than two inches high, bloom in profusion on the grasslands, or tundras, of the highest peaks.

Many ornamental shrubs, some of which withstand transplanting to urban environment, lend color and fragrance to the mountain area. In early spring, flowering currants gleam in masses of pale gold, and the thimbleberry is white with flowers resembling a single rose. The yellow flowers of the fly honeysuckle are surrounded by reddish leaves, and the wax flower blooms ivory white against deep emerald backgrounds. Glossy mountain laurel with rosy flowers—often called calico bush—mountain balm or ivy, native hawthorn, shrubby purple cinquefoil, mountain mahogany, and poison ivy form wild tangles that cover slopes and canyon floors. Three-leafed sumac and mountain sumac color the higher slopes with their massed scarlet foliage and dark red fruit clusters, while festoons of matrimony vine, woodbine, and red ozier, or dogwood, add their colors to the autumn foliage. On the slopes of the southern mountains the mock orange lifts its stiff branches and snowy blossoms.

Most of Colorado's mountain trees are coniferous and play an important part in minimizing erosion and helping to conserve water for lowland irrigation. Massed conifers act as giant reservoirs, storing up heavy snows so that they melt slowly. To protect these all-important watersheds, the Federal Government has set aside millions of acres of mountain land as national forests.

White firs, common on the lower slopes of central and southern Colorado, are dwarfed by dense forests of slender lodgepole pines farther north. The Douglas fir attains heights of 100 feet, soaring almost as high as the Alpine fir, and has a slender trunk, light spongy wood, and flat blunt leaves. The western yellow pine, often called bull pine, is considered Colorado's best timber tree, and is found everywhere in the higher mountain regions except in the northern part of the State. Ornamental bristle-cone pines grow on all the higher slopes.

Engelmann spruce and balsam fir, to be found up to timberline, grow in dense stands on cool exposures and are regarded as the best water conservers. The Douglas spruce frequents north slopes, and the majestic blue spruce, the unofficial State tree, is usually found near higher mountain streams. From the lower conifer belts to timberline grows the quaking aspen, known elsewhere as white poplar for its chalky white trunk. A broadleaf tree, it is especially beautiful in fall with its brilliant reds and yellows. It grows quickly from live roots and is the first to appear after forest fires.

Few Colorado trees are more striking than the sentinel timberline pines. Their dwarfed and gnarled limbs, appearing to writhe in torture, make them a favorite with painters and photographers. Known as "wind timber," they are living skeletons of the lumber, fox-tail, and bristle-cone pines which wage an unending fight with the cold fierce winds that sweep the alpine snow fields on the roof of the Continent.

As for animal life, early explorers found the Colorado mountains and plains abounding with herbivorous and predatory wild beasts, the chief food supply of the Indians. Slaughter by trappers and hunters, and encroachment of settlers upon their natural habitats, have tremendously reduced their numbers—in some instances, almost to extinction.

Before the coming of the white man, it has been estimated, some thirty million bison—described by Coronado as "large humped cattle, maned like lions"—roamed the plains and the level expanses of mountain parks; today, there remain only a few small protected herds. The antelope, once so numerous that hunters sold their carcasses by the wagon load, are certainly doomed unless adequate compensation is made for the rapidly diminishing open range. Only a few of these small, tawny, prong-horned animals now remain on the plains and lower foothills, so timid and fleet of foot that they are rarely glimpsed. The gray prairie wolf, enemy of buffalo and cattle alike, is virtually extinct; but its cousin, the coyote, seems to thrive in spite of all attempts to exterminate it.

Although agricultural and industrial expansion has swept the larger animals far back into mountain fastnesses, the plains and foothills are populated with a variety of interesting smaller creatures. Skunks of several kinds are to be seen—and avoided—from prairie to upper hills. Badgers, gophers, moles, and shrews abound, and on the plains is another squirrel-like rodent, the spermophile. Rabbits, cottontails and "jacks," both white and black tailed, are plentiful, and prairie dog "towns" flourish in spite of poison campaigns.

The greatest scourge of the prairie land is the grasshopper. The small green variety is native to the State, but most of the larger species migrated to Colorado when the land was put under cultivation; they range from the bulky "lubber," occasionally two inches long, to the small "Carolina locust." The damage done by these pests is tremendous; recent poison campaigns have yielded as high as five bushels of "hoppers" an acre; swarms of them now and again invade the cities like another Egyptian plague.

The official State bird, the black-and-white lark bunting, nests in the tall grass and yucca of the prairie and plateau lands. Desert horned lark and the highland plover, the latter far from the salt marshes and shore lines preferred by most of its kind, are common on the plains, as are the meadow lark, robin, and the sweet-voiced Western mocking bird. Overhead soars the rough-leg hawk, and the prairie falcon, joined at times by the carrion-eating turkey buzzard; at dusk the Western night hawk, or bullbat, wheels in the sky. Familiar to prairie travelers are the western horned owl and the white-rumped shrike, industriously catching grasshoppers and laying up a supply for future use by impaling them on thorns or the spikes of barbed-wire fences; the little burrowing owl bobs clownishly at the mouth of an abandoned prairie-dog hole, and the long-tailed magpie chatters shrilly among dusty cottonwoods.

Irrigation attracted a host of new birds, and as large areas of the plains are now cultivated fields, many varieties have migrated to these sections. Here are innumerable song sparrows, Western yellow throats, and both yellow-headed and red-winged black birds. In the marshlands are found at least eighteen species of wild duck, two of wild geese, and many varieties of wading birds. The grebe, or helldiver, appears in summer, and the loon is a winter visitor. The mourning or turtle dove, several kinds of swallows, and large numbers of a resplendent ringnecked pheasant, introduced from China, find Colorado an ideal home.

In the foothills are dusky grouse and dignified sage hens; in the seclusion of ravines the blue bird, the brilliant tanager, a variety of woodpeckers, and dozens of other birds brighten the shadows with flashing color. On the higher slopes lives the camp-robber, or Rocky Mountain jay; here also are the Rocky Mountain grosbeak, the hermit thrush, rosy finch, crossbill, and the boisterous brown nuthatch, said to be the only bird that descends a tree trunk head foremost. Broad-tailed and rufous humming birds are common; the latter, not much larger than an insect, winters in the tropics, spends a few weeks in the Colorado hills, and summers in Alaska. The gray dipper, or water ouzel, builds its oven-like nest among the spray-drenched rocks along mountain streams and plunges boldly into the water to catch fish. The white-tailed ptarmigan is the highest ranging of all Colorado birds, and white-throated swifts and the demure canyon wren also frequent the loftier ranges.

Bald or white-headed eagles are frequently sighted wheeling in the sky, but the graceful golden eagle, nesting on inaccessible crags, is more common. In the mesa country of the Western Slope the long-tailed crested road runner, or chaparral-cock, is often seen racing along the highway or engaging in deadly combat with its ancient enemy, the rattlesnake, which it kills just for the sport of it, apparently.

The larger carnivores of the mountain area, the mountain lion and the grizzly bear, once very numerous, have been all but exterminated by systematic hunting encouraged by large bounties. Forest rangers estimate that less than half a dozen grizzlies remain in the State. Black and brown bears are still rather numerous; the lynx, or bobcat, still prowls the hills. The Western red fox is found along timberline, but the mountain wolf, like the prairie lobo, is virtually extinct. The black-footed ferret, the Rocky Mountain weasel, and the dwarf weasel, the smallest true carnivore in Colorado, are found in scattered areas.

Through the aspen thickets in remote regions range herds of black-tailed or mule deer, frequently to be surprised close to mountain highways. Higher in the mountains, where snows are deep and fodder is scarce, elk thrive in an alien environment. Near timberline is the habitat of the protected and rarely glimpsed bighorn sheep.

Martens and porcupines live on the mountain slopes while along streams and lakes are Western mink, muskrat, and a few otter; partially submerged beaver "houses" dot less frequented watercourses. Rabbits of several varieties, notably Baird's snowshoe rabbit, live on the higher slopes.

Bats are found throughout the State; the little brown bat and the grayish big-eared bat arc the most common. Rats and mice, nocturnal by habit, are seldom seen during the day; but hollow logs and stumps, crevices in rock piles, ditches, weed borders, and marshes harbor myriads of them. Perhaps the most interesting of the small mammals is the diminutive cony, or pika, an odd rabbit-like creature found only in rock slides above timberline and unknown outside the State. For its practice of curing and storing hay in small stacks for winter use, it is known as the "Haymaker of the Heights." Black, gray, and brown squirrels disport themselves in the conifer forests; the ground squirrel, familiarly known as the chipmunk, is extremely tame and approaches close to mountain camps to pick up whatever choice bits can be found.

Colorado has its share of reptiles and amphibians, confined largely to the plains, foothill, and plateau country. Of the numerous varieties of lizards that slither over sun-warmed stones on hillside and in canyon, the most interesting is the horned lizard, miscalled the horned toad, sold in many curio shops, either mounted or alive. Many lakes near Denver and Boulder harbor painted turtles; the soft-shell and the yellow-necked mud turtle are found in the eastern rivers; and the land tortoise is common on the plains. Of native snakes only the prairie rattler, which occasionally strays into the foothills and lower mountains, is poisonous, although a few specimens of the deadly Western diamond-back have been found in the southern part of the State.

In all sections of the State are bugs and beetles, varying in size from the two-inch dark-shelled cockroach to the small round ladybird decked in her bright colors. Many beetles, armed with needle-like antennae, seriously damage trees and standing fields of grain. At least 243 species of parasitic plant lice and many different scale insects have been listed as unwelcome Colorado guests; regiments of energetic ants build their labyrinthian tunnels in sandy soil, under rocks, and around dead trees. The peculiar stick insect, resembling a miniature bamboo fishing pole with legs, is found in widely scattered sections. Myriads of gnats and mosquitoes emerge each summer from swamps and stagnant water on the prairies and in the high mountain parks. Mosquitoes of the Culicidae family, which carry malaria, are rare in Colorado, but the woodtick lurks in old fence posts, fallen timber, and shrubby under-growths, and is to be guarded against as a carrier of spotted fever.

Of the fifteen varieties of spiders, the crab spider, the jumping spider, and the wolf spider are common types; the venomous black widow is not a rarity. The giant tarantula of the plains, popularly believed to be poisonous, is harmless, as are all smaller members of its family. The many-legged centipede, which often—too often—secludes itself in boots or other unexpected places, lives along the eastern base of the foothills; in the Arkansas Valley specimens five inches long have been caught.

Butterflies, moths, and flies of many colors and varieties occur throughout the State. The more common butterflies are the mourning cloak, painted lady, milkweed, tortoise shell, and numerous swallowtails. Lightning bugs hover over the prairie meadows, and Colorado's dry sunny climate and abundance of flowers find favor with more than seven hundred kinds of bees.

Rivers and lakes throughout the State contain a great variety of fish. In lakes, reservoirs, and sluggish prairie streams are channel cat, bullheads, sucker, carp, and minnows. Colder mountain streams and lakes, fed by melting snows, are preferred by such hardy swimmers as perch, flat sunfish, sebago or landlocked salmon, and many varieties of silver or blue bass. And the pride of Colorado flash through these same waters—cutthroats, steelheads, speckled, Eastern brook, Loch Leven, and famed rainbow trout—names that bring a sparkle to every angler's eye. State and Federal hatcheries annually release many milllons of fingerlings in Colorado waters.