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has-i.e. the possession of the property under whatever muniments of title the vendor had, and a right to 'tack,' or add, the period of possession to make up the time necessary to gain absolute title by adverse possession. See ADVERSE POSSESSION; TITLE (to property).

because it favors the increased production of carbohydrates.

COLOR, IN PLANTS. The great majority of plants show distinct coloration, especially in aërial or aquatic organs. The absence of color is an index of parasitic or saprophytic life, but it must be borne in mind that many parasites and saprophytes are highly colored. The most common coloring matter in plants is chlorophyll, which manifests itself in various shades of green. Light of some strength has been shown to be necessary for the development of chlorophyll, though recent experiments show that it may develop in various seedlings germinated in perfect darkness, and that the synthesis of carbohydrates may take place vigorously under a dense layer of cork. The presence of plastids and favorable conditions of nutrition are neces

sary for the proper development of chlorophyll. Yellow coloration in plants is also commonly associated with plastids, and is due to the relative abundance of xanthophyll or carotin present as compared with the true chlorophyll. The phenomenon of yellowness is most common in dying leaves, and is especially well shown in autumn. However, in many young leaves, especially where the nutrition conditions are unfavorable, yellow leaves also appear. Unfavorable nutrition is probably the cause of yellow ness in most cases. In dying leaves the part near the veins usually remains green longest. In young leaves the green parts are longer and much better developed internally than are the yellow or white parts.

Red or blue coloration in plants is not directly associated with plastids, but is due to pigments that are scattered through the cellsap. The coloring substances are called anthocyans, erythrophyll if red, cyanophyll if blue. Blue colors occur most commonly in flowers, while the reds occur abundantly in leaves, as well as in flowers. The red coloration of leaves

has been much discussed in literature, and deserves further mention. While in some plants, as coleus, red colors are more or less permanent, in most cases redness is periodic. Perhaps the three most common examples of color display are: (1) in the young actively growing leaves of seedlings or perennial shoots; (2) in wintering leaves, especially of rosette plants; and (3) in dying leaves, especially in autumn leaves. All kinds of causes have been assigned to account for periodic coloration, but by far the most satisfactory is one proposed by Overton in 1899. He has shown experimentally that an excess of sugar in nutrient solutions causes an early and rich development of color, while an absence of sugar retards this development. In the summer the products of a day's photosynthesis are commonly carried off before another day begins; but in the cool autumn nights this transfer is checked, and sugars accumulated in the leaf unite with tannin substances and cause the production of the pigments. A similar explanation, plus the great flow of sap, would account for red leaves in spring. Mechanical injury, which prevents the carbohydrate transfer, also causes an excess of sugar and gives rise to red colors. Light seems to favor color development, perhaps

Much has been said as to the ecological significance of red colors. Stahl and Kny, as a result of experiments, hold that red colors increase the available supply of heat, and thus prolong the leaf activities in fall and enlarge them in spring. Kerner has also held the protective' theory of color. If red colors do have any such functionand this is by no means proved--it must probably be regarded as quite incidental. In no case can the need for protection be regarded as a cause of the development of pigment, as one might suppose from reading various treatises on the subject of color. See CHLOROPHYLL; PHOTOSYNTHESIS; LEAF. Consult Overton, "Beobachtungen und Versuche über das Auftreten von rothem Zellsaft bei Pflanzen," in Jahrbuch für wissenschaftliche Botanik, vol. xxviii. (Berlin,

1899).

COLORADO, kōl'ô-rä'dô (Sp., colored red)

(the Centennial State'). A State of the Amerision. It lies between latitudes 37° and 41° N., can Union, the twenty-fifth in order of admis and longitudes 102° and 109° W., and is bounded on the north by Wyoming and Nebraska, on the east by Nebraska and Kansas, on the south by Oklahoma Territory and New Mexico, on the miles; breadth, 275 miles; land area, 103,658 west by Utah. Length from east to west, 380 square miles; water area, 290 square miles.

watershed of the continent, and is, after WyoTOPOGRAPHY. Colorado lies upon the great ming, the most elevated State in the Union. A number of the most prominent ranges of the Rocky Mountain system traverse the State in a northerly and southerly direction, spreading magnificently over more than half the surface. The eastern section lies in the plain of the great Mississippi Basin, rising gradually from an ele

vation of about 3000 feet at the eastern bound

ary to a considerably higher altitude in the west. In the longitude of Denver and Colorado Springs the surface becomes broken by irregular chains of foot-hills. Back of these rise abruptly the lofty ranges of the Rockies. Entering the State from the north, they are called the Medicine Bow Range, and continue south as the Front Range to Pike's Peak, west of Colorado Springs. This is the most famous mountain in the State, but not the highest, being one of a score that range between 14,000 and 14,500 feet in elevation. West of these ranges are three valleys called North, Middle, and South Parks. North Park is inclosed on the west by the Park Range, and is separated from Middle Park by a ridge, extending from the east to the west, called the Divide. The North Platte River rises on its northern slope; on its southern, the Rio Grande. Between the Middle and South parks the Front Range meets the Saguache, the loftiest of them all. For miles its crest towers above the 13,000-foot level, surmounted by the impressive Holy Cross Peak, the Princeton, Harvard, Yale, and other mountains whose heights exceed 14,000 feet. To the southeast the range is continued in the Sangre de Cristo and Culebra, which extend into New Mexico. West of these latter ranges lies another valley called the San Luis Park, while In west of this rise the San Juan Mountains. the remainder of the western portion of the State there is a confusion of broken mountains, pla

teaus, and valleys, with a general slope to the westward.

Of the many mountain passes, 13 are over 10,000 feet in altitude, the Argentine reaching 13,286 feet. The great valleys or parks above mentioned inclosed by mountains are a distin guishing feature of the scenery. San Luis Park contains 8000 square miles (the most level land in the State, though elevated 7500 feet). Other important valleys are the Arkansas (q.v.), Rio Grande (q.v.), White Grande, and Gunnison. There are over 39,964 square miles of park and valley lands. The North Platte and South Platte unite to form the Platte of Nebraska. The source of the South Platte is 11,176 feet above tide, and its fall in the short distance to Denver is 6000 feet. The Arkansas rises 10,176

feet above the sea in the west central part of the State, rapidly falling to 7877 feet, and flows southeast and east into Kansas, pasing through the 'Royal Gorge' cañon, 3000 feet deep. The Rio Grande rises in the Saguache Range and flows through San Luis Park into New Mexico. The largest streams on the west are the Yampah and White, tributaries of the Green River, Utah; the Grand, one of the main affluents of the Colorado; and its tributaries, the Gunnison, Dolores, and San Miguel. None of these streams is navigable. No other State contains the headwaters of so large a number of rivers. The only lake of consequence, San Luis, about 60 miles long and a quarter of a mile wide, lies in San Luis Park, and receives several small streams, but has no visible outlet. The lofty peaks and deep-lying parks are equaled in grandeur by the river cañons; those of the Arkansas, Grand, Black Cañon of the Gunnison, Little Colorado, and Uncompahgre, varying in depth from 1000 to 3000 feet. A large area in Saguache County has been reserved as a State park.

CLIMATE AND SOIL. The high altitude of the State premises a cool temperature; but, save on the higher elevations, extremes are rare, the climate being generally mild and remarkably salubrious. The days are sometimes hot, but the nights are cool and free of humidity. The yearly mean temperature at Denver (5182 feet) in January is 28.2° F.; July, 71.7° F.; Pueblo (4675 feet), January, 28.7° F.; July, 74° F. Frosts do not occur until late in the autumn and disappear early in the spring; but snows are heavy and lasting on the mountains, yet in the low levels are seldom deep, and very soon melt

away.

The mean annual rainfall for the State is 14.8 inches. This fall, although light, is well distributed, and in many sections of the Great Divide' cereals are grown without irrigation. The heaviest rainfall is in the mountains. At Pike's Peak the mean precipitation is 29.7 inches; at Climax (10,304 feet), 34.8 inches. On the plains it is much less. At Denver the mean fall is 14.3 inches; at Colorado Springs (6032 feet), 14.5 inches; at Las Animas (3899 feet), 11.9 inches.

The atmosphere is so dry and pure that fresh meats are preserved by the simple process of dry ing. The late summer is almost rainless. The climate and air of Colorado are considered of great benefit to asthmatic and pulmonary sufferers, and the charming parks are likely to become the great natural sanatoriums of North

America. Thousands of people flock to Denver, Colorado Springs, and other sections of the State to regain their health. The various mineral springs are also adjuncts to the remedial nature of the climate. The hot sulphur springs of Middle Park and Wagon-Wheel Gap, and the hot iron and soda springs of Manitou, Cañon City, Glenwood Springs, and Idaho Springs are famous.

The soil along the river-bottoms is largely alluvial. In the eastern part of the State it is a light loam. In some places siliceous and micaceous substances abound, while here and there clay formations crop out. The forests of the State cover about 10,500,000 acres of land, and are restricted mainly to the mountains. For flora and fauna, see the paragraphs under ROCKY MOUNTAINS and UNITED STATES.

GEOLOGY. The geological structure of Colorado is extremely varied. In the less elevated region east of the Rocky Mountains, Cretaceous and Tertiary strata are exposed in nearly horizontal position and in great thickness. On the eastern flank of the Rocky Mountains these strata are succeeded by older sediments, including Silurian, Carboniferous, and Jura-Trias, which are upturned and in places intensely folded. The axis of the mountain system is formed by granites and other igneous rocks, more or less metamorphosed, of Archæan age, with a great variety of later volcanic rocks. On the western edge of the system Paleozoic strata again appear, and are overlaid in the extreme western part of the State by Cretaceous, Jura-Trias, and Tertiary beds. The Carboniferous rocks, unlike those along the Appalachian Mountains, inclose no coal-seams. Coal occurs, however, in great abundance in the Laramie group of the Cretaceous. The great upheavals accompanied by volcanic activity along the Rocky Mountains have favored the formation of ore deposits, some of which are of great economic importance. Cripple Creek on the slopes of Pike's Peak, Leadville, Boulder, Ouray, Rosita, Silverton, Gilpin, Lake City, and Gunnison are important centres of gold, silver, and lead mining. Copper, zinc, manganese, and iron ores also occur in extensive deposits.

MINING. Colorado is best known as a mining State, ranking first in the mining of precious metals. The value of its gold and silver output in 1906 was almost one-fourth the value of the tion of gold increased in value from $4,150,000 in total output in the United States. The produc

1889 to $28,760,000 in 1900; in 1906 it was about

$30,600,000. In 1897, for the first time, the gold product exceeded that of California, while the output for 1906 was a fourth larger than that of the rival State. About two-thirds of the gold production in 1906 was from the Cripple Creek district. Silver-mining reached its maximum output in 1892, and then decreased until 1895; since which time it has slightly increased. The commercial value of silver mined in 1906 was $7,840,000. Colorado for a number of years was the leading State in the production of lead. In 1896, however, it was surpassed by Idaho, and in 1902 fell behind Utah. In 1905 the output amounted to 53,806 short tons as against 82,137 in 1900. Coal is mined in sixteen different counties, the largest producers being Las Animas and Huerfano Counties. The output of bituminous coal in 1906 was 11.240,078 short tons, valued

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COPYRIGHT, 1907, BY DODD, MEAD & Co.

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