AGAVE, an extensive genus of plants belonging to the natural order conaryl ltdacex. The species have large, fleshy leaves, with teeth ending in spinous points. From the center of a circle of these leaves there rises, as the plant ap proaches maturity, a tall scape of flowers. The idea that the agave blos soms but once in a hundred years is a fable. But as a result of this popular misconception the plant is known under the name of Century Plant. What really happens is, that some species, taking many years (10 to 70, it is thought) to come to maturity, flower but once, and then die. The plant originally belonged to North America and is chiefly found hi Mexico. It is now cultivated in the south of Europe.
AGE, any period of time attributed to something as the whole, or part, of its duration: as the age of man, the several ages of the world, the golden age.
In Physiology.—If the word age be used to denote one of the stages of human life, then physiology clearly distinguishes six of these: viz., the periods of infancy, of childhood, of boyhood or girlhood, of adolescence, of manhood or womanhood, and of old age. The period of infancy terminates at 2, when the first dentition is completed; that of childhood at 7 or 8, when the second dentition is finished; that of boyhood or girlhood at the com mencement of puberty, in temperate cli mates from the 14th to the 16th year in the male and from the 12th to the 14th in the female; that of adolescence extends to the 24th year in the male and the 20th in the female; that of manhood or woman hood stretches on till the advent of old age, which comes sooner or later, accord ing to the original strength of the con stitution in each individual case, and the habits which have been acquired during life. The precise time of human ex istence similarly varies.
In Archmology.—The Danish and Swedish antiquaries and naturalists, MM. Nilson, Steenstrup, Forchamber, Thom sen, Worsaae, and others, have divided the period during which man has existed on the earth into three—the age of stone, the age of bronze, and the age of iron. During the first-mentioned of these he is supposed to have had only stone for weapons, etc. Sir John Lubbock divides this into two—the palwolithic, or older, and the neolithic, or newer, stone period. At the commencement of the age of bronze that composite metal became known, and began to be manufactured into weapons and other instruments; while, when the age of iron came in, bronze be gan gradually to be superseded by the last-mentioned metal. (Lyell's "The An tiquity of Man"; Lubbock's "Prehistoric Times.") In Law, the time of competence to do certain acts. In the United States, both males and females are of full age at 21. The age at which minors may be
punished or may marry varies in the several States.
Age of Animals.—The duration of life in animals is generally between seven and eight times the period which elapses from birth till they become adult; but this rule, besides being vague and indefinite, is quite useless in practice, because it af fords no scale of graduation which would enable us to ascertain the precise age of individuals.
Age of Plants.—Plants, like animals, are subject to the laws of mortality, and, in many cases, have the period of their existence determined by nature with as much exactness as that of an insect. It is principally to annual and biennial plants that a precise period of duration is fixed. The remainder of the more per fect part of the vegetable kingdom, whether herbaceous, or shrubby, or ar borescent, consist of plants which may be classed under two principal modes of growth. One of these modes is to in crease, when young, in diameter, rather than in length until a certain magnitude is obtained, and then to shoot up a stem, the diameter of which is never materially altered. The addition of new matter to a trunk of this kind takes place by the in sinuation of longitudinal fibers into the inside of the wood near the center; on which account such trees are called en dogenous, or monocotyledons. The other mode is, from the beginning, to increase simultaneously in length and diameter, but principally in length. The addition of new matter to a trunk of this kind takes place by the insinuation of longi tudinal fibers into a space beneath the bark, and on the outside of the wood, near the circumference; on which account such trees are called exogenous, or dicotyle dons. The way by which the age of ex ogenous trees may be computed is by cut ting out a portion of their circumference, Ind counting the number of concentric rings that are visible; the woody cylinder of one year being divided from the suc ceeding one by a denser substance, which marks distinctly the line of separation of the two years. In consequence of the ex treme inequality in thickness of the an nual layers of wood on opposite sides of a stem, a person judging of the whole age of a tree by the examination of the layers of the stunted side only would commit errors to the amount of 60 per cent., and more.
AGEN (a-zhon' a town of France capital of the department of Lot-et-Ga ronne, on the right bank of the Garonne, on the railway from Bordeaux to Tou louse. Its situation though rather un healthy, makes it the entrepOt of the com merce between Bordeaux and Toulouse. The town is very ancient, seat of a bishop, and possesses a cathedral dating back to the 6th century. Pop. about 25,000.