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INERTIA

923

INFUSORIA

public industrial schools is needed. The

first commission on industrial and technical education in Massachusetts made a report in 1906, in which it was advocated that a commission be appointed for a term of years to provide industrial schools independent of the existing public schools, to be adapted for boys and girls of from 14 to 16 years of age. These schools are to be supported by the municipality, aided by the state in proportion to local expenditure. Such a commission has been appointed, with Mr. C. H. Morse as secretary, and with it the first public system of industrial schools in the U. S. was established in 1907-.

Iner'tia, a general property of matter, in virtue of which all bodies tend to remain in their present state of motion or of rest. Inertia is the Latin word for laziness; but the laziness of matter is such that it hesitates to stop, when once set in motion, quite as much as it hesitates to start, when once at rest. Used quantitatively, inertia is equivalent to mass or quantity of matter. Newton showed that the inertia of a body is strictly proportional to its weight, and hence we measure the inertia of a body by weighing it Hicks and others have invented balances by which the inertia of bodies may be compared without weighing them; and this is the really fundamental method of measuring the quantity of matter in a body. See DYNAMICS.

In'fantry. See ARMY.

In'floresc'ence. Flowers either may occur solitary upon plants> or they may be collected together in a definite region of the plant body, which region is then termed the inflorescence or flower-cluster. Flowering plants, the re- ' fore, have then flowers either solitary or in an inflorescence. Great attention has been paid to the various forms of inflorescence, since they are quite constant in different plants, and are really serviceable in dibtinguishing them. The various flower-clusters are not always easy to separate, as they pass gradually into one another, but the prominent forms are easily distinguished. There are two general types of inflorescence, known, as the "botryose" and "cymose" types. In the botryose type the lowest flowers are the oldest, the buds being above, and the flowers continue to bloom upward in what is called acropetal succession, that is, toward the apex. In the cymose type this order is re versed .t the first flower being the terminal one and the buds successively arising below, the succession of blooming being basipetal, that is. toward the base of the plant The botryose forms of inflorescence

A, spike1 B, compound raceme, C, compound umbel; Z?,nead.

are mucft more numerous and various than the cymose, The prominent botryose types are: "Raceme," in which the flowers are distributed upon an elongated axis, each upon its own pedicel, as in spring beauty; "panicle," which is really a compound raceme, in which the fiower stalks branch again as in the spray-like clusters of grasses; "Thyrsus," a compact pyramidal panicle, as the lilac or a cluster of grapes; "Corymb," in which the lower flower stalks are elongated, thus bringing all the flowers up to a level, resulting in a flat-topped cluster; "Umbel," in which the axis is shortened and the numerous pedicels arise from the same point, like the ribs of an umbrella, resulting in a flat-topped cluster, as in the common carrot, the name umbel being derived from its umbrella-like form; "Spike," in which the flowers are sessile along an elongated axis, as in the plantain; "Spikelet," a small spike or one member of a branching spike, the name being applied chiefly to the smaller clusters in the grass inflorescence which go to make up the spike or panicle; "Head," in wrhich the flowers are sessile or nearly so upon a shortened or broadened axis, as in the sunflower, dandelion etc.; "Ament" or "Catkin," in which the flowers on the elongated axis are subtended by conspicuous bracts which overlap one another and completely cover them, as in the pussy willow, birch, alder etc.; "Spadix?" in which the axis becomes fleshy, bearing minute sessile flowers, and is more or less overarched by an enormous bract known as the "spathe," as in Jack-in-the-Pulpit, calla lily etc.

It will be noticed that certain definite relations exist among these forms, so that they may be referred to one another easily. The raceme seems to be the more primitive type of inflorescence, and the others are more or less modifications of it. For example, the corymb is a raceme in which the lower pedicels are elongated, so that a flat-topped cluster is produced; an umbel is a raceme in which the axis has been much shortened, so that the pedicels are thrown together; a spike is a raceme in which the flowers are sessile; a spadix is a fleshy, spike; a head is an umbel with sessile flowers, while a catkin or ament is a spike with unusually conspicuous bracts. The cymose inflorescence is chiefly represented by the cluster known as a "cyme," a flat-topped cluster resembling the corymb; but the central flowers, that is, the uppermost, bloom first, so that the succession of blooming is toward the outer part of the cluster, as in the common elder.

JOHN M. COULTER.

In'fuso'ria* microscopic animals common in stagnant water and in infusions of vegetable and animal substances. Formerly, certain microscopic plants, which have the power of movement, were confused with them, and a genera] term animdlcula was used to designate aiJ microscopic life. The