G u A 



[ 208 ] 



GYP 



GYMNOSPE'EMIA. (from 7^1/09, nudus, 

 naked, and aTepfia, semen, seed.) 

 The first order in the fourteenth 

 class, Didynamia, in Linnaeus's 

 artificial system ; having four naked 

 seeds in the bottom of the calyx, 

 with the exception of one genus, 

 Phryma, which is monospermous. 



GYNA'NDBIA. (from <yw?}, a woman, 

 and avrjp, Gr. a man.) The name 

 of the 20th class in Linna3us's 

 sexual system, consisting of plants 

 with hermaphrodite flowers, having 

 the stamens growing upon the 

 style, or having the stamina united 

 with, or growing out of, the pistil, 

 and either proceeding from the 

 germen or the style. The orders 

 of this class are taken from the 

 number of the pistils, but botanists 

 are not agreed as to the admission 

 of some of them into the class. 



GYNA'NDROUS. A term applied to a 

 particular class of plants, in which 

 the stamens and pistils are united. 

 The orders of this class depend on 

 the number of the anthers. 



GY'PSUM. (<yvyfros, Gr. gypsum, Lat. 

 gypse, Fr. gesso, It.) The chaux 

 sulfatee of Brongniart and Haiiy. 

 Sulphate of lime ; it is composed of 

 sulphuric acid 46, lime 33, water 

 21. It is insoluble in acids, and 

 does not effervesce like chalk and 

 dolomite, the lime being already 

 combined with sulphuric acid, for 

 which it has a stronger affinity 

 than for the other acids. It pos- 

 sesses double refraction. There is 

 one variety known by the name of 

 anhydrite, or anhydrous gypsum, 

 which contains no water. Sulphate 

 of lime is an abundant mineral 

 salt, presenting itself under various 

 forms, crystallized or otherwise. 

 From gypsum is obtained plaster 

 of Paris, the gypsum being burnt 

 in a kiln, and the water thereby 

 driven off. The varieties of gypsum 

 are numerous ; the crystallized 



. transparent varieties are known as 

 selenite j the fibrous and earthy as 



gypsum; and the granular and 

 massive as alabaster. The salt 

 mines of this country afford ex- 

 amples of nearly all the varieties. 

 The white powder obtained by 

 exposing gypsum to a strong heat 

 has obtained the name of plaster of 

 Paris, from the extreme abundance 

 of this mineral in the neighbour- 

 hood of that capital. Its inferior 

 hardness, together with its chemical 

 characters, will serve to distinguish 

 it from the carbonate, fluate, and 

 phosphate of lime. " The gypsum 

 formation consists of alternating 

 beds of gypsum and argillaceous 

 and calcareous marl, which are 

 regularly arranged, and preserve 

 the same order of succession where- 

 ever they have been examined. 

 The gypsum forms three distinct 

 masses. The lowest consists of 

 thin strata of gypsum containing 

 crystals of selenite, which alternate 

 with strata of solid calcareous marl, 

 and with argillaceous shale. The 

 middle is like the lowest mass, 

 except that the strata of gypsum 

 are thicker, and the beds of marl 

 are not so numerous ; it is chiefly 

 in this mass that fossil fish are 

 found. The uppermost mass is the 

 most remarkable and important of 

 all j it is in some parts more than 

 seventy feet thick ; there are but 

 few beds of marl in it ; the lower 

 strata of gypsum in this mass have 

 a columnar structure. In this 

 upper mass of gypsum the skeletons 

 and scattered bones of birds and 

 unknown quadrupeds are discover- 

 ed. Remains of turtles and croco- 

 diles have been also found in the 

 same strata." For a further and 

 more interesting detail, see Bake- 

 well' s Introduction to Geology. 



GYROCA'RPTJS. In botany, a genus of 

 plants containing few species, but 

 these widely distributed. 



GYRO'ETJS. (from ryty>oe, round, and 

 o$o vs, a tooth, Gr.) A genus of 

 fossil fishes, established by Agassiz, 



