H AB 



H^M 



arranged in small plates, representing 

 united teeth. These plates are repro- 

 duced as soon as destroyed by use. 



GY'MNOSPERMS (71/^1/69, naked, 

 o-Trep/ia, seed). A class of plants which 

 agree in all respects with Exogens, ex- 

 cept that their ovules, instead of being 

 enclosed in a pericarp, are exposed naked 

 to the fertilizing influence of the pollen, 

 as in the Coniferae and the CycadaceaB. 

 See Angeiospermia. 



GYN^CE'UM {'ivvaiKeiov, the wo- 

 man's part of the house). A term ap- 

 plied by Roper to the entire female sys- 

 tem of plants, with reference to the fan- 

 ciful language of Linnaeus. It is com- 

 monly called the pistil, and comprises 

 the ovary, the style, and the stigma. See 

 Androceum. 



GYNA'NDRIA {-^wrj, a woman, lLvi]p, a 

 man). The twentieth class in the Lin- 

 naean system of plants, in which the 

 stamens are situated upon the style, 

 above the ovary, as in passiflora. 



GY'NOBASE (-yi/i/J/, a woman, /Sciatr, 

 a base). A term applied to the recep- 

 tacle in plants, when it is dilated and 

 supports a row of carpels, which have an 

 oblique inclination towards the axis of the 

 flower, as in Labiatae, Boraginaceae, &c. 



GY'NOPHORE {'ivv\], a woman, ^epw, 

 to bear). Thecaphore. A term applied, 

 in Botany, to the stalk upon which the 

 ovary is sometimes seated, instead of 

 being sessile, as in tacsonia. 



GYNOSTE'MIUM {yw'rj, a woman, 

 arrjuav, a stamen). A term applied by 

 Richard to that condition of the filaments 

 in Orchidaceae, in which they are com- 

 bined into a solid body called the 

 columna. 



GY'PSUM {'iHoi, chalk; from 7^, 

 earth, et^w, to bake). Sulphate of lime; 



a modification of limestone, with a granu- 

 lar or crystalline texture, forming beds 

 and irregular masses, and, when highly 

 burned, constituting plaster of Paris. 

 There are two species, according tp 

 Jameson,— the prismatic, and the axi- 

 frangible. 



GY'RATE (7i;p69, curved). Curved 

 in from apex to base, as the fronds of 

 ferns; a term synonymous with circi- 

 nate. 



GYRA'TION {gyrus, a circle). The 

 act of turning round a centre, in the 

 manner of a wheel. The centre of gyra- 

 tion is that point in a revolving body, 

 into which, if all its matter could be col- 

 lected, it would continue to revolve with 

 the same energy as when its parts were 

 in their original places. 



Gyration, circle of. A wheel in 

 motion may be considered as an indefi- 

 nite number of pendulums, each of which 

 has its own centre of oscillation. If the 

 wheel be nearly balanced, these several 

 points of oscillation will accommodate 

 themselves so as to form, in their con- 

 tinued motion, a set of points equally 

 distant from the rim. These are centres 

 of gyration, and in their junction they 

 will form a circle of gyration. 



GYRO'GONITE {yvpos, curved, yoi,'r}, 

 seed). A term applied to the fossil seed- 

 vessel of plants of the genus Chara, found 

 in fresh-water deposits. The name was 

 derived from the idea that they were 

 shells of polythalamous cephalopods. 



GYRO'MA (Yi/poc, curved). Gyrus, 

 A term sometimes used as synonymous 

 with the annulus of the theca of ferns. 

 It is also applied to the shield, or trica, 

 of lichens, the surface of which is covered 

 with sinuous concentric furrows. 



H 



HAA'RKIES {haar, German, hair). 

 A designation of capillary pyrites occur- 

 ing in very delicate acicular crystals. 

 The term is also applied by German 

 mineralogists to a native sulphuret of 

 nickel. 



HABITATION. A technical term em- 

 ployed in botany to indicate generally the 

 country where a plant grows wild. It 

 must be distinguished from the term 

 station. The study of stations has been 

 styled the topography, that of habitations 

 158 



the geography, of botany. Thus, the 

 station of a plant may be a salt-marsh, 

 in a temperate climate, a hill-side, the 

 bed of the sea, or a stagnant pool. Its 

 habitation may be Europe, North Ame- 

 rica, or New Holland between the tropics. 

 See Station. 



HtE'MATITE {aina, blood). Blood- 

 stone ; a native oxide of iron, so named 

 from its blood-red streak. The red 

 haematite is an anhydrous, the brown a 

 hydrated, peroxide. 



