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BOOT. 283 BOOT TUBERCLES. ways, and for various railroad companies. His greatest prominence at the bar was due to his being retained as counsel for William M. Tweed in tlic 'Tweed rin<;" trial: for .Tudge Hilton in the Stewart will case; and for Hamilton Col- lege in the Fayerweather will case. From 18S3 to 1885 he was United States District Attorney in New York City. In 18iH) he was appointed Sec- retary of War to succeed Russell A. Alger. In this capacity he planned the new War College and a moditication of the rules of promotion, by which seniority ceased to be the sole claim. An- other reform was the institution of the general statf. He continued in office during ilcKinley's second administration and under President Roose- velt until the summer of 1903, when he resigned and was succeeded by William H. Taft (q.v.). ROOT, George Freoekick (1820-95). An American musician and composer. He was born at Sheffield, Mass., and studied music under George J. Webb of Boston, after which he taught music in New York City (1844-45), where he was organist of the Church of the Stranger. In 1859 he became a member of the Chicago music firm of Root & Cady. He composed many pop- ular songs and battle songs, notably "Battle Cry of Freedom," "Tramp, Tramp, Tramp," "Just Before the Battle, Mother," and the quartet, "There's Music in the Air," besides which he edited numerous books of sacred music. Other works were the cantatas Flotcer Queen (1852) ; Daniel (1852); The Pilgrim Fathers (1854); Bclshaz::ar's Feast (185G); and The Haymakers (1857). ROOT BARNACLE. See Rhizocephala. ROOT PARASITES. Plants attached to the roots of other plants, whose elaborated food they consume. They are usually without chlorophyll. In temperate climates the best known are proba- bh' broom rape and cancer root ; in tropical countries, Rafflesia (q.v.). Many species of Scrophulariaceoe and the Indian pipe (ilonotro- pa nniflora) are semi-parasitic. ROOT PRESSURE. If while a plant is rapidly absorbing water by the root sj'stem, it be decapitated, water will soon ooze from the stump — a phenomenon known as bleeding. The amount may be measured and the pressure under which it escapes may be ascertained. Since the pressure thus determined was first recognized as arising in the root system, the name root pressure was given to it. Since investigation shows, however, that cells of suitable character, located in any part of the plant, under proper conditions may develop a similar pressure, the terms .sap pressure and bleeding pressure are superseding it. Sap pres- sure is dependent upon the osmotic pressure (see Osmosis) of active cells which adjoin xylem bundles (see Anatomy), into which water es- capes and travels to the point of exit under the pressure of additional quantities of water from behind. There is no satisfactory explanation of the action of the cells which thus force water into the xyleni. Root pressure shows itself most strikingly in the spring before the leaves are fully developed, when the sap often exudes from wounds, as in grapevines and many trees, in considerable quantities. After the development of the foliage and under conditions which iiermit transpiration (q.v.). root pressure becomes less Vol. XVII.— 19. or disappears. It is, therefore, not uu iin|iortant factor in lifting water when water is most iiecdej. The amount of water which may escape iit often much greater than the volume' of the root system. Thus, in two and a half days, the slump of a stinging nettle gave olV over" eleven litem APPABATC8 TO UKASCBE BOOT FRRSMCRE. t, T-tube attai-'hed to stutiip of plant, filled with water and clost'd by Healing in llanie the tiii of c ; nt. a mtT- cur.v pressure tcauge conneeted with t. registering the fi.ree with which water is forced from the stump, s, a HUpport. (11 quarts) of water,*more than eight times the volume of the root system. A twelve-year-old birch in seven days exuded from an opening in the trunk 30 liters of water. When the central bud is cut out, various s))ecies of century plant exude water several months. A vigorous plant is said by Humboldt to yield as much as 1000 liters. The extrusion of water from the sugar maple in late winter or early spring is at first not due to root pressure, but rather to the expansion of gases in the twigs which are warmed during the sunny days. See Sap. ROOT TUBERCLES. Irregular swellings upon the roots of Leguminos.T, the alder, and a few other plants. They are due to an infection by various bacteria, or bacteria-like organisms. The ability of plants to assimilate the free nitro- gen of the air was a subject of discussion among agricultural chemists for many years. Georges Ville seems to have been one of the first to main- tain that certain plants can so assimilate, hut he did not discover the true explanation. The claim of 'illc was attacked by Boussingault. I.awes and Gilbert, and other.s. whose experiments seemed to give opposite results. Later llellriegel (q.v.) proved, by carefully conducted experi- ments, that clovers and similar crops enrich the soil by adding nitrogen to it and that they ob- tain this nitrogen from the air. and subsequent studies show that the bacteria gain entrance through the root-hairs. The action is recipro- cal; the plant furnishes the carbohyilrates nei>- essarv for the growth of the bacteria, which.