Germination

[Lat. germinatio, from germin are, to put forth, to bud.] ( Bot.) The proce by which a plant is produced from a seed. The phenomena of G. are best observed in dicotyledonous seeds, such, for instance, as the bean, pea, łup in, . These seeds consist of two lobes or cotyledons, enveloped in a common membrane; when this is removed, a small projecting body is seen, which is that part of the germ which afterwards becomes the root, and is termed the radicle. The other portion of the germ is seen on carefully separating the cotyledons, and is termed the plumule; it afterwards forms the stem and leaves. When the ripe seed is removed from the parent plant it gradually dries, and may be kept often for an indefinite period without undergoing any change; but if placed under circumstances favorable to its G., it soon begins to grow; these requisite circumstances are a due temperature, moisture, and the presence of air. Where these are present, the seed gradually swells, its membranes burst, and the germ expands. The root is at first most rapidly developed, the materials for its growth being derived from the cotyledons; and when it shoots out its fibres or rootlets, these absorb nourishment from the soil, and the plumula is developed, rising upward in a contrary direction to the root, and expanding into stem and leaves. For this growth the presence of air is requisite; if it be carefully excluded, though there may be heat and moisture, yet the seed will not vegetate. Hence it is that seeds buried very deep in the earth, or in a stiff clay, remain inert, but on admi ion of air by turning up the soil, begin to shoot forth. From experiments which have been made upon the G. of seeds in confined atmospheres, it appears that carbonic acid is evolved, and that part of the starch of the cotyledons pa es into gumand sugar; so that most seeds, as we see in the conversion of barley into malt, become sweet during G. Light is injurious to the growth of a seed. It is, therefore, obvious that the different requisites for G. are attained by placing a seed under the surface of the soil warmed by the sun's rays, where it is moistened by its humidity and by occasional showers, and excluded from light, but within reach of the acce of air. The most favorable temperature is between 60° and 80°; at the freezing point none of the more perfect seeds vegetate; and at temperatures above 100° the young germ is usually injured. Certain chemical changes, the most important being the conversion of starch into sugar, take place in the seed, and the embryo is nourished by the products of these changes. Thus nourished, it increases gradually in size, and ultimately bursts through the integuments of the seed. Its lower extremity, or radicle, is commonly protruded first, and, taking a downward direction, becomes fixed in the soil. The opposite extremity soon elongates upwards, and is terminated above by the plumule or gemmule, which is the first terminal bud, or growing apex of the stem; and at the same time the cotyledonary portion is either left under-ground, or is carried upwards to the surface. During the gradual development, the embryo continues to be nourished from the matters contained in the albumen or cotyledonary portion, and is ultimately enabled to produce its first leaves and root. The young plant is then in a position to acquire the nece ary nourishment by itself, for its further support and growth, from the media by which it is surrounded; and being rendered independent of the seed, has no need of the cotyledonary portion, which accordingly perishes. The spores of acotyledonous plants develop roots indifferently from any part of their surface: this mode of G. is termed heterorhizal. In the G. of monocotyledonous embryos, the radicle is not itself continued downwards so as to form the root, but it gives off branches of nearly equal size, which separately pierce its extremity and become the rootlets. Each of these rootlets, at the point where it pierces the radicular extremity, is surrounded by a cellular sheath, termed the coleorhiza. This mode of G. is commonly termed endorhizal. The radicle of a dicotyledonous embryo is itself prolonged downwards by cell multiplication just within its apex, to form the root; and this mode of G. is distinguished as exorhizal. See ROOT; STEM. Ger'minative, a. Relating to germination. Geroco'mia, Geroc'omy, n. [Fr. gérocomie, from Gr. ger on, an old man, and komein, to take care of.] (Med.) That part of the science which relates to the diet and treatment of old age. Gerona, (jai-rõna,) (anc. Gerund a ,) a fortified city of Spain, prov Catalonia, cap. of correg. of the same name, at the foot of a steep mountain on the Ter, 50 m. N.E. of Barcelona. It has a fine cathedral and other churches, which were sacked by the French under Augereau, during the Peninsular War, when the city stood a siege of seven months. G. is of great antiquity, and formerly gave the title of prince to the elder son of the kings of Aragon. Manuf . Coarse woollen and cotton stuffs and stockings. Pop . 14,085.- The corregidor ship, or sub-prov. of G. is very fertile, and has an area of 4,400 sq. m., with a pop . of 342,067. Ger'rardstown, in W Virginia, a P.O. of Berkeley co. Ger'ron. See GARON.