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CONDORCET. 261 CONDUCTION. CONDORCET, kuN'dOi'sa', JIarie Jean An- TOiXE Xicoi.A.s Caritat, Jlaiquis de (1743-94). A French mathematician and philosopher. He was born at Ribeniont, was educated by the ■Jesuits, won distinction for mathematics in his youth, and became an active member of the Acad- emy of Sciences in ITOil. Gonial, susceptible, and enthusiastic, he became allied with the advanced thinkers and shared in the economic and religious propaganda of Turgot, D'Alembcrt, and Voltaire. He took an active part in the Encyclopedic, and, on the strength of his graceful Eloges des aca- dciniciens marts avant JG99 (1773), he was made the perpetual secretary of the Academy of Sciences in 1777. He became a member of the French Academy in 1782. His Elements dii cal- cul des prohabilitcs (1785), revised and en- larged in a jiosthumous edition (1804), was his most important contribution to mathematics. From this time politics claimed him in increas- ing measure. He wrote a life of Turgot (1786), and of Voltaire (1787), and was chosen member of the Xational Assembly from Paris, becoming secretary of that body, and in February, 1792, its president. He composed several of its most important addresses, and elaborated a scheme of public instruction. Though finding Louis XVI. guilty, he refused to vote for his execution. He was active in framing the Constitution submitted to the Convention in February, 1703, but his op- position to the Terrorists led them to proclaim him an outlaw. Friends found him a refuge with a JIme. Vernet, who said "the Convention could declare him outside the law, but not out- side humanity." Tracked hither at last, he es- caped, was captured at Clamart, and died in prison at Bourg-la-Reine, March 29, 1794, from apople.y, exhaustion, or poison. While with Mme. Vernet he wrote the Esquisse d'un tableau liistorirjue des p7-ogrcs de I'esprit liumain, a declaration of human perfectibility through emancipation from priests and rulers, narrow in its sensationalist philosophy and fanatic in its anti-spiritualism, but interesting for its militant optimism. Condorcct's Works (Paris, 1847-49) contain a Life by Arago. Consult Morley, Criti- cal Miscellanies (London, 1893). CONDOTTIERI, kon'do-tya're (It., plur. of ccndotticre, captain, leader). The name given in Ital.y in the Middle Ages to the leaders of com- panies of military adventurers who ofl'ered their services to any party in any contest for pay and often practiced warfare on their own account, for the sake of plunder. The name is frequently applied also to the members of their companies. These mercenaries were called into being by the endless feuds of the Italian States during the Middle Ages. Among the most celebrated of their leaders were Sir John Hawkwood (c.l320- 94), the commander of the famous White Com- pany, who, after taking an important part in the wars between England and France, crossed into Italy and became Captain-General of Flor- ence; Carmagnola (c.1390-1432) . who fought in the pay of Jlilan and Venice; and Francesco Sforza ' (1401-66), who in 14.50 made himself Duke of Milan, to the exclusion of the lawful heirs of the Visconti. Venice began to employ cnndottieri in 1143; but their time of greatest activity was in the fourteenth and fifteenth cen- turies. Machiavelli paints them in the most tm- favorable light, and states that sometimes battles were fought by two eondottieri in which no one was killed except by accident. Consult Ricotti, titoria dcUc coinpagnie di Ventura (Turin, 1845). CONDUCTING TISSUE. In botany, the lines, strands, or groups of conducting cells used for transferring water and foods from one part of the plant to another. See Conduction. CONDUCTION (Lat. conductio, union, from condiieerc, to lead together, from com-, together + ducere, to lead, connected with Goth, tiuhan, AS, icon, OHG, siohan, Ger, ziehen, to draw). In botany, a. term applied to the transfer of water, foods, and other materials from one part of the plant body to another. In the smaller plants a sufficient amount of water can be supplied to cover evaporation and other needs, and the foods can be transferred, by relatively slow processes of dif- fusion and osmosis (qq.v.). In the larger plants, however, the amount of water and foods to be moved, and the relatively great distances to be traversed, have brought about the development of a system of tissues, arranged in elongated strands or in layers, specially adapted to facilitate trans- fer, and known as the conducting system. These are for water chiefly the xylem, or wood bundles, and for foods chiefly the phloem, or bast bundles, or perhajis the latex vessels. The xylem and phloem bundles are usually associated, running side by side in the stems, the xylem eitlier toward the centre, or with a phloem bundle also on the central side of it, or surrounded by the phloem. In the roots the primary xylem bundles are be- tween the phloem bundles, but by secondary thick- ening with age the same position as in stems is reached. So frequent is this association that the two bundles are usually described as re- gions of one fibrovascular bundle ( q,v, ) . These bundles form a connected system of strands, con- tinuous, through the stem, from youngest root to youngest leaf. In the leaves the bundles run in the larger ribs, and constitute the smaller veins, becoming more and more slender. The final branches join with others to form a fine network, or end blindly among the green tissues, the xylem biindles being the last to disappear. The Xyij:m and Water-Conduction. The essential elements of the xylem are the trachete or Iracheids, with which parenchyma cells and wood fibres are usually associated. The tracheids are cells whose walls have become imequally thick- ened as they mature; their protoplasm finally disappears, leaving only the empty cell-wall. The tracheae are similar, except that a large number of the end walls, where the elements of a row abut, have been resorbed, so that the cell-cham- bers, empty as they finally become, communicate freely. The tracheae, where best developed, are thus long tubes, half a millimeter (1-50 inch) or less in diameter, and 1 to 3 meters (3 to 10 feet) long. The remaining elements of the xylem are of less importance for conduction, ( See Anat- omy, ) Through the xylem bundles the water absorbed by the roots travels to the leaves and other surfaces, from which it is evaporated. The water first enters the root-hairs or the adjoining surface cells of the root (see Absorption and Root) ; thence it traverses the cortex and enters the tracheary tissue, and travels along it to its destination. Proofs that the xylem bundles are the path of the transpiration stream are found by girdling and by the use of colored solutions. When the xylem bundles are severed the leaves wilt promptly, while all the other tissues of the