Page:The New International Encyclopædia 1st ed. v. 04.djvu/665

* CHEMOTROPISM. 583 CHENAVARD. siiie on which retarilation occurs becomes con- cave; the oi>i)ositc siilo convex. If a root is posi- tively cheiiiotropir toward a substanee, that side which conies in contact with the most of the sub- stance — as the latter diffuses through the medium in which the root is growing — will be retarded in growth and become concave. If the root is negatively chemotropic, acceleration of growth will take the place of this retardation, and that >ide will become convex. Thus the root- tiji is turned either toward or away from the source of the diffusing compound, and the bend- ing continues until all sides are c(iually stimu- lated. What the mechanism of this response is lias not lK>en made out. It ,is probable that the difference in absorption of the stimulating sub- stance on the two sides is accountable for the change in growth, but further than this we can- not go. The reaction is seen in case of many gases, liquids, and solids when dissolved in water. The term aerotropism (q.v.) has been applied to the power of responding to gases in this way. A good example of chemotropism is furnished by the following: If fungi be grown in a plate of moist gelatin, and an e.xcessiof sugar be added to a certain part of the gelatin plate, the filaments will bend and grow from all parts of the medium toward the part which is richer in sugar. The diffusion of the sugar from this re- gion out into the surrounding material is the oc- casion of the response. Also, certain fungi which grow upon decaying meat (e.g. Saprolegnia) are similarlj- attracted by meat extract. Another e.aniple occurs in the fly -catching sundew (Drosera). The tentacles upon its leaves ex- hibit chemotropism toward nitrogenous com- pounds and toward ammonium phosphate to a very m.irkcd degree. CHEMULPO, Korean seaport. See Korea. CHEMUNG (she-mung') GROUP. A series of sandstones and shales of marine origin, consti- tuting the uppermost member of the Devonian system in southern and western Xew York and eastern Pennsylvania, and deriving its name from the Chemung Xarrows, near Elmira, N. Y., where the formation was first described. The Chemung group formed the top of the 'New Y'ork system' of the early Xew York Slate (ieologi- eal Sur-ey. It succeeds the Portage group, which it conformably overlies, and which it re- sembles in the shallow-water character of most of its deposits. The rocks are mostly shales, though sandstones are frequent, and a pudding- stone bed, known as the Panama Conghmierate, occurs in the western part of Xew York, at a horizon about 230 feet below the top of the group. In the vicinity of its original locality, near Klniira, the Chemung group has a thickness of about 1500 feet; it thins westward toward the Penn>ylvania-hio line, where it disappears. To- ward the east it changes its character, the marine deposits giving way to the estuarine and brack- ish-water deposits of its littoral facies, the Catskill group (q.v.). Southward, through eastern Pennsylvania, the thickness of the marine deposits increases, and along the northern .p- palachian Mountains the group is from 3.500 to 5000 feet thick. Its southward contimuition be- low Pennsylvania has not been w<]l dcternuncd. The Cheiming rocks, as a rule, abound in fossil contents. Prachiopods are most abundant, in places forming whole layers of rock, where the shells were washed together by currents and strewn over the shallow bottoms. Land plants, prophetic of the forms seen in the later coal- measures, are common in the more easterly por- tions of the formation, especiallj- in the estuarine beds of the Catskill series, where a large fern, Arch.Topteris (q.v.), is often found. At -several localities in western Xew York have been found large numbers of Dictyospongidsc (q.v.), allies of, and probably when alive just as beautiful as, the modern glass-sponge t Ihiplectella) . The characteristic fossils are; Brachiopods — Spiri- fcr disjunctus, Atrypa hystrix. and A. spinosa, Kh_TichonelIa contrada, I'roductella lachrymosa; Peleeyiiods — Pterinca cliemungensis, Grammysia subarcuatus, Prorhynchus nasutum, Schizodus cliemungensis. Some phj-llocarid Crustacea have been found, and in a few localities 'fish-beds' have yielded good examples of Holoptyc'hius, Bothriolepis, etc. The economic products of the Chemung consist of building-stone, and oil and gas in the western counties of Xew York. BiBLiOGR.PiiT. Williams, '"On the Fo.ssil Fau- nas of the Upper Devonian, etc.," in Bulletin Yo. 3 of the United States Geological Survey (Wash- ington, 1884); "On the Fossil Faunas of the Upper Devonian: The Genesee Section," in Bulle- tin No. 4 of the United States Geological Sur- veil (Washington, 1887) ; Prosser, "The Classifi- cation and Distribution of the Hamilton and Chemung Series of Central and Eastern Xew York," Part I., in Forty-ninth Annual Report Xciv York State Museum, Vol. II. (Albany, 1898) ; Part II., op. cit. 51.st, Vol. II. (Albany. 1899) ; Stevenson, "The Chemung and Catskill on the Eastern Side of the Appalachian Basin," in Proceedings American Association- Advance- ment of Science, Vol. XL. (Salem, 1891). See, al.so. Devonian System ; Catskill CiRoup ; Clay ; Brkk; Oil; Gas; Petroleum. CHE'NA (Hind.). The Hindu name of the most common and widespread species {Ophio- crphnlus striatus) of the 'walking* or serpent- lieadcd fishes. See WAITING FiSHES. CHENAB, che-nab' (Pers., gathering of waters). The largest of the five rivers which give name to the Punjab (q.v.), British India (ifap; India, B '2). It rises at an altitude of 14,000 feet above the sea in the western Hima- layas, flows through the Ritanka Pass, and. after a southwest direction, enters the plains of the Panjab, at Riasi. It receives from the right the .Theiam, and from the left the Ravi and the Ghara. with its affluents, the Sutlej and the Beas. After its junction with the filiara. near Uchh, it assumes the name of the Panjnad (five rivers), ana flows into the Indus, near Mithankot. Its length is about T.iO miles. In the lower part of its course it is from a half-mile to one mile in breadth. It is navigable by rafts 50 miles below Riasi. CHENAVARD, slia'nA'viir', Paul Joseph ( 1808-!1.") I . . French historical painter, bom in Lyons. He was a pu])il of Ingres and Dela- croix, and began for the Pantheon a series of historical frescoes, interrupted by the reversion of the structure to the Church. Such portions as were executed are now in the ^lusetim of Lyons. His other works include ''Deatli of Cato and of Brutus." Consult Silvcstre, "Etude sur Paul Chenavard." in his Histoire des artistes vivants (Paris, 1855-56).