AGA'P'E, a genus of plants belonging to the natural order, Amaryllidaceee. The species are known by the immune of American Aloes, and produce clusters of long stiff fleshy leaves, collected in a circle at the top of a very short stem, and bearing flowers in a long terminal woody nape. With Doreen rats and Yucca it forms in the natural order A maryllidaeve an instance of high development both in vegetation and fructification, compared with what is more generally characteristic of that tribe. If a Crinum or an Amaryllis had the stein elongated into a woody trunk, instead of being contracted into a short disk, lying at the bottom of a scaly bulb, the affinity between them and Agarc would at once be obvious.
There are many species of this genus, one only of which requires to be mentioned.
Agave Americana, or the American Aloe, is a plant which, when full grown, has a short cylindrical woody stem, which is terminated by hard, fleshy, spiny, shnrp-pointed, bluish green leaves, about six feet long, and altogether resembling those of the arboreseent aloes. Each of there haven will continue to exist for many years, so that but a small number have withered away by the time the plant has acquired its full maturity. It is commonly supposed that this occurs only at the end of one hundred years ; hut this, like many other popular opinions, Is an error ; the period at which the Agave arrives at maturity varying, according to circumstances, from ten to fifty, or even seventy years. In hot or otherwise favourable climates, it grows rapidly, and arrives sooner nt the term of its existence ; but in colder regions, or under the care of the !gardener, where it is frequently impracticable to attend to all the circumstances that accelerate its development, it requires the longest period that has been assigned to it. Having acquired its full growth, it finally produces its gigantic flower-stem, after which it perishes. This stem is sometimes as much as 40 feet high, and is surrounded with a multitude of branches arranged in a pyramidal form, with perfect symmetry, and having on their points clusters of greenish-yellow flowers, which continue to be produced for two or three months in succession. The native country of the American Aloe is the whole of America within the tropics, from the plains nearly on a level with the sea, to stations upon the mountains at an elevation of between 9000 and 10,000 feet. From these regions it has been transferred to almost every other temperate country ; and in Italy, Sicily, and Spain, it has already combined with the date and the palmetto to give a tropical appearance to European scenery.
Independently of its beauty and curiosity, this plant is applicable to many useful purposes. Its sap may be made to flow by incisions in the stem, and furnishes a fermented liquor called by the Mexicans Pulque ; from this an agreeable ardent spirit, called Vino Mercal is distilled. The fibres of its leaves form a coarse kind of thread, and are brought to this country under the name of Pita Flax ; the dried flowering stems are an almost impenetrable thatch ; an extract of the leaves is made into balls, which will lather water like soap ; the fresh leaves themselves cut into slices are occasionally given to cattle ; and, finally, the centre of the flowering stem split longitudinally is by uo means a bad substitute for a European razor-strop, owing to minute particles of silica forming one of its constituents.
AGE. The term of human existence is divisible into distinct periods, each of which is distinguished by characters peculiar to itself. These characters, as far as they are external, are obvious to every one ; but these external characters depend on internal states which are not obvious, and which have been discovered only by careful and perse vering research. And the curious and interesting facts which those researches have disclosed, show that the different epochs into which life is divided are not arbitrary distinctions, hut arise naturally out of constitutional differences in the system, dependent on different physiologieal conditions. The natural epochs of human life are six, namely, the period of infancy, childhood, boyhood or girlhood, adol escence, manhood or womanhood, and old age. The space of time included in the first four of these periods is fixed. In all persona after the lapse of a certain number of years, a definite change in the system uniformly takes place, in consequence of which the peculiarities which distinguish one period give place to those which characterise the Succeeding. Thus the period of infancy, commencing at birth, extends to the end of the second year, the point of time at which the first dentition is completed : the period of childhood, commencing at the close of the second year, extends to the termination of the seventh or eighth year, the point of time at which the second dentition is com pleted : the period of boyhood or girlhood extends from the seventh or eighth year to the commencement of the age of puberty ; that is, in general, in this country, in the female, from the twelfth to the fourteenth year, and for the male, from the fourteenth to the sixteenth year : the period of adolescence extends from the commencement of the period of puberty to the twentieth year of the female, and the twenty-fourth of the male : the period of womanhood extends from the twentieth, and of manhood, from the twenty-fourth year, to an age neither determined nor determinable with any degree of exactness ; because the point of time at which mature ago lapses into old age differs in every individual. It differs in many cases by a considerable number of years ; and it differs according to primitive constitution, to the management of early infancy and childhood ; according to regimen, exercise, occupation physical and mental, and the several other circumstances included under the general term 'mode of life.' It is, an observation familiar to every one, that some persons are older at fifty than others are at seventy, while instances every now and then occur in which an old man who reaches his hundredth year retains as great a degree of juvenility as the majority of those who attain to eighty. The period extending from the age of thirty or forty to that of extreme old age is then the only variable period in the term of human existence; the only period not fixed by limits which it is beyond the power of man materially to extend or abridge.