USED IN NATURAL HISTORY. 



51 



head. Applied to those univalve 

 shells in which the apex or head 

 is worn off, in the progress of 

 growth. 



DECOMPOSE. When the chemical 

 constitution of substances is al- 

 tered, they are said to be decom- 

 posed. In a strict mineralogical 

 sense, the term is only applicable 

 to the result of chemical action 

 which occurs spontaneously. Cer- 

 tain ores of iron, &c., in which 

 sulphur predominates, decompose 

 on exposure to air. 



DECOMPOUND. Applied to those ra- 

 mifications of plants which are va- 

 riously compounded as to leaves, 

 in which the petiole bears second- 

 ary petioles. When the second- 

 ary petioles are divided into a 

 third set, such leaves are said to 

 be supradccompound. 



DECOR'TICATED Disbarked ; with- 

 out bark. Divested of epidermis 

 or skin : worn. 



DE'CREMENT. When the planes of 

 crystals decrease equally to a point, 

 they are said to arise from a sim- 

 ple decrement ; but when they do 

 not decrease equally on all sides, 

 the decrement is compound. 



DECRE'PITATE. When a mineral, 

 on exposure to heat, flies with a 

 crackling noise, it is said to decre- 

 pitate. 



DKCUMA'NTTS. Lat. Tenth. Huge, 

 fair, of a large size. 



DECU'MBENT. fr. lat. deaimbo, to lie 

 down. Lying prostrate but rising 

 from the earth at the upper ex- 

 tremity: applied to the directions 

 taken by plants. 



DECUHHENT. fr. lat. decurro, to run 

 down. Dccursive. Running down: 

 applied to leaves which are pro- 

 longed down the stem, giving it a 

 winged appearance. 



DECCRSIVE. Having a tendency to 

 run down. 



DECUSSA'TION. fr. lat. decusso, to 

 cross like an X. Applied to parts 

 which cross each other, as leaves 



on a stem, when arranged in pairs 

 which alternately cross each other. 

 Also, to the lines or striae on shells 

 which intersect each other. 



DEFLEXED. Turned downwards. 



DEFOLIATION. Shedding leaves in 

 proper season. 



DEFRA'NCII. Lat. Of Defrance. 



DEGRADE. fr. lat. de, priv.; gradus, 

 step, degree. To lessen, to cut 

 down. 



DEGRADA'TION. The act of lessen- 

 ing; reduction. 



DEGLUTI'TION. fr. lat. deglutire, to 

 swallow. The act by which sub- 

 stances are passed from the rnouth 

 into the stomach, through the pha- 

 rynx and oesophagus. 



DEIII'SCENT. fr. lat. dehiscere, to gape 

 wide open. Applied to the spon- 

 taneous separation of the valves 

 of certain fruits for the discharge 

 of the seeds. 



DEINOTHE'RIUM. SeeDinotherinm. 



DEJECTIONS. Matters evacuated 

 from the bowels. 



DELIQ,UE'SCENCE. fr. lat. deliquesco, 

 to melt away. Becoming liquid 

 by absorbing moisture from the 

 air. When a panicle is so much 

 branched that the primary axis 

 disappears, it is said to be deli- 

 quescent. 



DEL'TA. The Gr. letter A. The 

 triangular deposits, shoals or isl- 

 ands, found at the mouths of cer- 

 tain rivers are called deltas. 



DE'VTOID. fr. gr. A, delta ; eidos, 

 resemblance. A form of leaf. 

 (Fig. 46, p. 41, Book vii). 



DELTO'IDEA. -Lat. fr. gr. letter A, 

 eidos, resemblance. Resembling 

 a delta A. (p. 65, Book viii). 



DELPHI'NULA. Lat. A little dol- 

 phin. Name of a genus of shells 

 of the family of troohoides. 



DELPHI'NUS. Lat. Dolphin. A ge- 

 nus of aquatic mammals. 



DEL'PHIS. The name of a priestess 

 of the temple of Delphos, which 

 Linnaeus gave to an animal of the 

 order of cetacea. 



